Diagnostic Utility of CK5/6 and TTF-1 in Subtyping Non-Small Cell Lung Carcinoma: Experience from a Tertiary Care Centre

Diagnostic Utility of CK5/6 and TTF-1 in Subtyping Non-Small Cell Lung Carcinoma: Experience from a Tertiary Care Centre | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Diagnostic Utility of CK5/6 and TTF-1 in Subtyping Non-Small Cell Lung Carcinoma: Experience from a Tertiary Care Centre Zainab Ashfaque Ali, Namita Goyal, Gunjan bhatia, Archana dodiyal This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8305530/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Introduction: Accurate subtyping of non-small cell lung carcinoma (NSCLC) is essential for therapeutic decision-making. Small biopsies often present diagnostic challenges, making immunohistochemistry (IHC) crucial. This study evaluated the histopathological spectrum and diagnostic utility of CK5/6 and thyroid transcription factor-1 (TTF-1) in NSCLC cases. Materials and Methods: This cross-sectional study was conducted over 18 months in the Department of Pathology, RNT medical college. Sixty-four NSCLC cases diagnosed on histopathology were included. Specimens were processed routinely, stained with Hematoxylin & Eosin, and subjected to IHC for CK5/6 and TTF-1. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated. Results: Before IHC, SCC, ADC, and NSCLC–NOS accounted for 46.88%, 32.8%, and 20.3% of cases, respectively. After IHC, SCC increased to 62.5%, ADC to 37.5%, and NSCLC–NOS reduced to 0%. CK5/6 showed sensitivity 79.2%, specificity 95%, PPV 90.5%, NPV 88.4% (p < 0.0001). TTF-1 showed sensitivity 75%, specificity 100%, PPV 100%, NPV 70.6% (p < 0.0001). Conclusion: The combined use of CK5/6 and TTF-1 significantly improves NSCLC subclassification, eliminating the NSCLC–NOS category. Routine application in small biopsies can enhance diagnostic accuracy and guide therapy. Biological sciences/Cancer Health sciences/Diseases Health sciences/Oncology Non-small cell lung carcinoma CK5/6 TTF-1 Immunohistochemistry Histopathology Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Lung cancer, a global public health menace, exerts a profound impact on society. It stands as the most prevalent cancer worldwide, accounting for 1.76 million cancer-related deaths annually¹,². The disease exhibits a marked gender bias, affecting males nearly twice as often as females³. In India, lung cancer ranks as the second most common cancer among males and sixth among females, and is the fourth leading cause of cancer-related mortality following breast, cervix, and lip–oral cavity cancers⁴,⁵. Accurate diagnosis and classification of lung cancer require small tissue samples, typically obtained via bronchoscopy, percutaneous image-guided techniques, or from metastatic sites. Cell block preparations from malignant pleural effusions also serve as valuable diagnostic tools⁶. However, challenges arise with minute biopsies, making immunohistochemistry (IHC) crucial for histological categorization, forming the foundation for molecular investigations and treatment strategies⁷. IHC is widely available, cost-effective, and can be performed on small samples, aiding in tumor subtyping and biomarker assessment⁸. NSCLC accounts for about 85% of lung cancers and is further subtyped into adenocarcinoma (ADC) and squamous cell carcinoma (SCC)⁹. Histological evaluation alone can be challenging, hence the utility of IHC markers such as CK5/6 (for SCC) and TTF-1 (for ADC) ¹⁰, ¹¹. This study assesses the role of these markers in accurately subtyping NSCLC in small biopsies from a tertiary care hospital in Southern Rajasthan. Materials and Methods Study Design and Setting: This cross-sectional study was conducted in the Department of Pathology, R.N.T. Medical College, Udaipur, over a period of 18 months (October 2023 to April 2025). Ethical approval was obtained from the Institutional Ethics Committee of R.N.T. Medical College, Udaipur (Approval No.: 2024/810). All methods were performed in accordance with the relevant guidelines and regulations, including the Declaration of Helsinki. Written informed consent was obtained from all participants prior to inclusion in the study. Sample Size: Sixty-four NSCLC cases diagnosed on histopathology were included. Inclusion Criteria: • Patients of all ages and both sexes • Adequate clinical and imaging assessment • Specimens obtained via bronchoscopy, image-guided percutaneous biopsy, or cell block preparations Exclusion Criteria: • Benign and infective lung lesions • Secondary (metastatic) lung malignancies • Inadequate biopsies (autolyzed or scant samples) Procedure : Lung biopsies were fixed in 10% neutral buffered formalin, processed, embedded in paraffin, sectioned at 3–4 μm, and stained with Hematoxylin & Eosin (H&E). Immunohistochemistry (IHC) was performed using the LEICA BOND MAX Premium system. CK5/6 cytoplasmic positivity in ≥50% of tumor cells indicated squamous cell carcinoma (SCC), while TTF-1 nuclear positivity in >50% of tumor cells indicated adenocarcinoma (ADC). Statistical Analysis: Data were analysed using SPSS software. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated. A p-value <0.05 was considered statistically significant. OBSERVATION AND RESULTS A total of 64 cases of NSCLCs were analysed in this study. All of them were biopsy specimens, obtained via bronchoscopy, percutaneous methods guided by imaging and cell block preparations. Age and gender distribution The age of the cases of NSCLC ranged from 23 to 85 years, with the mean age being 62.14 years. The maximum number of cases were in the age group of 61 to 70 years (20 cases, 31.25%). There was a clear male predominance; out of 64 cases, 50 (78.1%) were males and 14 (21.9%) were females. A comparison of age distribution and gender revealed male predominance across all age groups. Among the 14 females, the most common age group was 61 to 70 years, followed by 71 to 80 years. Among the 50 male cases, 39 (78%) were above 50 years, and only 11 (22%) were below 50 years of age (Table 1) Table 1: Age and gender distribution Age Male (n=50) Female (n=14) Total (n=64) 21-30 1 1 2 31-40 1 1 41-50 9 9 51-60 12 1 13 61-70 15 8 23 71-80 11 4 15 81-90 1 1 Tumour site There were more cases in the right lung (38 cases, 59.4%) compared to the left lung (20 cases, 31.2%). In 6 cases (9.4%), the tumor was diagnosed on cell block material, and the exact anatomical location could not be determined.In the right lung, the tumor was located in the upper lobe in 25 cases (65.8%), middle lobe in 4 cases (10.5%), lower lobe in 9 cases (23.7%)In the left lung, the tumor involved the upper lobe in 15 cases (75%), lower lobe in 5 cases (25%). ( Table 2): Distribution of cases based on laterality and location Right lung n=38 Left lung n =20 Cell block n=6 Upper lobe=25 upper lobe=15 Middle lobe=4 lower lobe =5 Lower lobe= 9 Histological type of tumour prior to IHC As per the records in the histopathology department, the 64 tumours had been initially typed histologically according to the WHO Classification of Tumours of the Lung, Pleura, Thymus and Heart (4th edition). The most common histological type of lung carcinoma was squamous cell carcinoma (SCC) (n = 30, 46.9%), followed by adenocarcinoma (ADC) (n = 21, 32.8%) and non-small cell lung carcinoma – not otherwise specified (NSCLC, NOS) (n = 13, 20.3%). Table 3: Histological types of NSCLCs before using IHC Squamous cell carcinoma Adenocarcinoma Non small cell (unclassified) Total 30 21 13 64 IHC staining pattern in the different types of NSCLCs On application of immunohistochemical (IHC) stains, a total of 40 cases showed CK5/6 positivity, confirming the diagnosis of squamous cell carcinoma (SCC). Among these, TTF-1 positivity was observed in 3 out of 40 SCC cases (7.5%), but the staining intensity was weak in all three cases. These cases were still classified as SCC due to strong CK5/6 positivity and supportive squamous morphology.-1 positivity in 24 cases, Immunohistochemical (IHC) staining showed TTF-1 positivity in 24 cases, supporting the diagnosis of adenocarcinoma (ADC). TTF-1 alone was positive in 19 cases, while CK5/6 expression was observed in 7 out of 21 cases (33.3%). Among these, five cases showed focal or weak staining, and two cases demonstrated strong positivity. Despite CK5/6 expression, these cases were classified as adenocarcinoma based on their predominant glandular morphology and strong TTF-1 immunoreactivity, rather than squamous differentiation. Histological type of tumour after IHC The tumours were reclassified after immunohistochemistry with TTF 1 and CK5/6 . Those tumours which showed nuclear positivity for TTF 1, negative staining for CK5/6 were typed as adenocarcinomas. (Figure 2, A-D) The histological type of majority of the cases was squamous cell carcinoma 40 cases. The tumours which had strong cytoplasmic and membranous positivity for CK5/6 and negative staining for TTF 1 were classified as Squamous cell carcinoma (Figure 1, A-D). The NSCLC were recategorized as follows: Those with a Hand E diagnosis of squamous cell carcinoma, but IHC staining positive for TTF 1, were grouped as NSCLC favouring adenocarcinoma (Figure 2A- D). Those with a Hand E diagnosis of adenocarcinoma, but IHC staining positive for CK5/6 and showing negative staining for TTF1 were grouped as NSCLC favouring squamous cell carcinoma (Figure 1 A-D). 13 H and E diagnosed NSCLC NOS were recategorized as 8 squamous cell carcinoma and 5 cases of adenocarcinoma based on their positive staining for CK5/6 and TTF1 respectively. The frequency distribution of the histological type of NSCLC after IHC is given in (Table5) Table 5 : Histological type of tumour after IHC Histological type after IHC No. of cases Percentage Adenocarcinoma 19 29.68% NSCLC favouring adenocarcinoma 5 7.81% Squamous cell carcinoma 32 50% NSCLC favouring squamous cell carcinoma 8 12.5% Total no. of cases 64 100% Squamous cell carcinoma remained the commonest type of NSCLC after IHC. The number of cases increased (from 30 to 40) while those of adenocarcinoma increased from 21to 24 cases out of a total of 64 cases of NSCLCs. Table 6: Significance of adding immunohistochemistry in the diagnosis of non-small cell lung cancer (NSCLC) (n=64) Tumour typing based on HPE diagnosis Morphological diagnosis (n=64) (%) After using IHC (CK5/6 and, TTF 1) n (%) Subtype characterization ADC 21 (32.8%) 24 (37.5%) Increment by 14.29% SCC 30 (46.88%) 40 (62.5%) Increment by 33.33% NSCLC-NOS 13 (20.3%) - Complete reduction Table 7: Performance of individual markers TTF 1 and ck5/6 in IHC proven adenocarcinomas and NSCLC favouring adenocarcinoma Sensitivity Specificity PPV NPV P value CK5/6 79.2% 95% 90.5% 88.4% <0.0001 TTF1 75.0% 100% 100% 70.6% <0.0001 Using morphological diagnosis as the screening test and IHC as the gold standard, the analysis revealed the following: CK5/6 exhibited a sensitivity of 79.2%, specificity of 95.0%, positive predictive value (PPV) of 90.5%, and negative predictive value (NPV) of 88.4%. TTF-1 showed a sensitivity of 75.0%, specificity of 100%, PPV of 100%, and NPV of 70.6%.The statistical association for both markers was highly significant with p-values < 0.0001, reinforcing their diagnostic utility in differentiating adenocarcinoma and squamous cell carcinoma in NSCLC. DISCUSSION Lung cancer continues to be a major global health concern due to its high mortality rate, underscoring the importance of accurate tumor classification (12). Since the WHO 2015 update, and more definitively in the WHO Classification of Thoracic Tumours, 5th edition (2021), histological subtyping using immunohistochemistry (IHC) has become mandatory in biopsy reporting to ensure appropriate treatment selection. In this context, the present study aimed to reclassify NSCLC cases initially diagnosed on morphology alone using the updated WHO guidelines. In our study, the age of patients with NSCLC ranged from 23 to 85 years, with a mean age of 62.14 years. Similar findings were documented by Singh et al. (mean age 58.1 years) and Rao et al. (range 35–90 years, mean 58.4 years), both highlighting the higher prevalence of NSCLC in elderly males (12,15). The peak incidence in our cohort occurred in the 61–70-year age group (35.93%), consistent with earlier reports by Nair CK et al. and Malik et al. (16,17). Squamous cell carcinoma (SCC) cases in our study ranged from 39 to 87 years (mean 51.6 years), comparable to data from Coimbatore, where the majority of SCC cases were between 61 and 70 years, with a mean age of 65.5 years (21). Adenocarcinoma (ADC) cases ranged from 23 to 78 years (mean 44.4 years), slightly younger than reported in Western literature, where ADC frequently presents even below 40 years of age (18–20). A clear male predominance was noted, with a male-to-female ratio of 3.57:1, in agreement with several Indian studies summarized in Table 18. Smoking remains strongly associated with SCC, as demonstrated by landmark studies from Krishnamurthy et al. (25) and Santos-Martínez et al. (26), which reported a higher incidence of SCC among male smokers. In the present study, all IHC-proven SCC cases occurred in males, aligning with established evidence relating smoking to SCC pathogenesis (27–29). Among the 24 adenocarcinoma cases, 60% were males and 40% females, similar to previous findings (21). When stratified by gender, SCC predominated in males (57.44%), whereas ADC was slightly more common among females (54.54%). Regarding tumor location, our study showed a slight predominance of right-sided lesions, with the upper lobe being the most commonly involved. Similar observations have been made by Kumar SB et al. and Rawat J et al. (30,31). Studies from AIIMS, New Delhi, have also highlighted the upper lobe as a frequent site of involvement (24). In our cohort, ADCs were predominantly located in the upper lobe, while SCCs more frequently involved the lower lobe. Before IHC, 46.88% of cases were diagnosed as SCC, 32.8% as ADC, and 20.3% as NSCLC-NOS. After applying the recommended IHC markers (CK5/6 and TTF-1), all 13 NSCLC-NOS cases were reclassified—eight as SCC and five as ADC—completely eliminating the NSCLC-NOS category. This resulted in a final distribution of 62.5% SCC and 37.5% ADC, corresponding to an increase of 33.33% in SCC and 14.29% in ADC diagnoses after IHC. This improvement aligns with previous studies that have demonstrated the significant impact of IHC in reducing NSCLC-NOS diagnoses (32). These results are comparable to earlier reports (Table 19). Globally and within India, SCC has historically been the predominant NSCLC subtype, as noted in studies from Ahmedabad, Bareilly, Jaipur, and Uttarakhand (33–36). Our study also reported a higher proportion of SCC (62.5%), consistent with similar regional findings. Although recent literature indicates a shift toward increased detection of ADC since 2012 (38), particularly in Western populations, SCC continues to predominate in many Indian cohorts. This difference is likely attributable to regional variations in smoking patterns and environmental exposures. The introduction of sensitive markers such as TTF-1 for ADC and CK5/6 for SCC has further improved diagnostic accuracy, supporting the WHO 2021 recommendations advocating the use of a limited but specific IHC panel (12). For statistical purposes, ADC and NSCLC favoring ADC were considered together as adenocarcinoma, while SCC and NSCLC favoring SCC were grouped under squamous cell carcinoma. On initial H&E evaluation, 43 of 64 cases (67.19%) were correctly classified, while 21 cases (32.81%) required reclassification after IHC. Among the 21 histologically diagnosed ADC cases, 13 retained their diagnosis, 2 were reassigned as NSCLC favoring SCC, and 5 of the NSCLC-NOS cases were reclassified as ADC, yielding a final total of 24 ADC cases (37.5%). Similarly, eight NSCLC-NOS cases and two ADC cases were reclassified as SCC, resulting in a total of 40 SCC cases (62.5%) (P = 0.000). These findings parallel those from AIIMS Delhi (Ritika W et al.) and studies by Loo et al., Walia et al., and Pelosi et al., all of which reported significant reclassification of NSCLC-NOS following IHC (32,43). Evaluation of immunohistochemical marker expression demonstrated CK5/6 positivity in 62.5% of cases and TTF-1 positivity in 24 cases. Among the initially diagnosed ADC cases, 5 showed both TTF-1 positivity and weak CK5/6 expression, while 13 demonstrated strong TTF-1 positivity alone. One case with strong CK5/6 expression was reclassified as NSCLC favoring SCC. A similar predominance of CK5/6 expression was reported by Shweta et al., where 40 of 58 cases showed positivity (33). In our study, CK5/6 demonstrated a sensitivity of 75%, specificity of 100%, PPV of 100%, and NPV of 64.3% for identifying SCC. TTF-1 exhibited a sensitivity of 72.2%, specificity of 95%, PPV of 86.7%, and NPV of 88.4%. These values align well with previous studies, where TTF-1 sensitivity and specificity ranged between 75% and over 95% (13,39 ,40). Similar trends for CK5/6 have been reported by Keneng Chen et al. (sensitivity 78.9%, specificity 97.7%) (41) and Wang et al. (2020) (sensitivity 77.05%, specificity 96.44%) (42). Among the histologic ADC cases, 2 of 21 (9.52%) showed CK5/6 positivity and were reclassified as SCC, while the remaining 19 (90.47%) cases demonstrated TTF-1 uptake and were categorized as ADC. The higher specificity of CK5/6 compared to its sensitivity parallels findings from earlier studies and underscores its utility as a reliable marker for SCC. Declarations Author Contribution Dr. Zainab Ashfaque Ali was responsible for the conception and design of the study, collection of data, analysis and interpretation of results, and preparation of all tables, figures, and statistical outputs. Dr. Zainab Ashfaq Ali also wrote the primary draft of the manuscript and coordinated the overall research work.Dr. Namita Goyal contributed to manuscript preparation, provided critical academic input, and supervised the study with important intellectual guidance and revisions.Dr. Gunjan Bhatia actively assisted in data analysis, verification of results, and preparation of tables and figures, and contributed to the technical refinement of the study.Dr. Archana Dodiyal assisted in data compilation and supported the preparation of the research work.All authors critically reviewed the manuscript and approved the final version. Data Availability All data generated and analysed during the current study are included in this article and its related information files. The de-identified raw dataset (Master Chart) used for the analyses is available in related information files. The Authors received NO FUNDING for this work" References Bray F, Ferlay J, Soerjomataram I, Siegel RL, Torre LA, Jemal A. Global cancer statistics 2018: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA Cancer J Clin. 2018;68(6):394–424. Sung H, Ferlay J, Siegel RL, Laversanne M, Soerjomataram I, Jemal A, et al. Global cancer statistics 2020: GLOBOCAN estimates of incidence and mortality worldwide. CA Cancer J Clin. 2021;71(3):209–49. NCRP (National Cancer Registry Programme), ICMR. Report of National Cancer Registry Programme 2020. Bengaluru: ICMR-NCDIR; 2020. Varghese C, Sebastian P. Lung cancer in India: current status and future perspectives. Curr Opin Pulm Med. 2022;28(4):250–7. Travis WD, Brambilla E, Nicholson AG, Yatabe Y, Austin JHM, Beasley MB, et al. The 2021 WHO classification of lung tumors. J Thorac Oncol. 2021;16(9):933–47. Travis WD, Brambilla E, Noguchi M, Nicholson AG, Geisinger KR, Yatabe Y, et al. Diagnosis of lung cancer in small biopsies and cytology: implications of the 2015 WHO classification. Ann Oncol. 2015;26(8):1207–15. Mukhopadhyay S, Katzenstein AL. Subtyping of non–small cell lung carcinoma: a practical approach for small biopsy specimens. Arch Pathol Lab Med. 2009;133(7):1089–98. Turner BM, Cagle PT, Sainz IM, Zhai QJ, Pryzwansky KB, Dacic S. CK5/6 and p63 are complementary in the diagnosis of pulmonary squamous cell carcinoma. Am J Surg Pathol. 2012;36(5):634–41. Tacha D, Zhou D, Cheng L. TTF-1 monoclonal antibodies: clone dependence and high sensitivity/specificity for lung adenocarcinoma. Appl Immunohistochem Mol Morphol. 2011;19(2):115–9. Moreira AL, Mukhopadhyay S, Allen TC, Beasley MB, Borczuk AC, Chen G, et al. AAIHDP recommendations for optimal pathologic evaluation of lung cancer biopsy specimens. Arch Pathol Lab Med. 2020;144(3):284–99. Yatabe Y, Kerr KM, Utomo A, Rajadurai P, Du X, Chou T-Y, et al. EGFR mutation testing practices in lung cancer: current status in Asia. J Thorac Oncol. 2015;10(3):412–6. Organisation mondiale de la santé, Centre international de recherché sur le cancer, editors. Thoracic tumours. 5th ed. Lyon: International agency for research on cancer; 2021. (World health organization classification of tumours). Wiener RS, Schwartz LM, Woloshin S, Welch HG. Population-based risk for complications after transthoracic needle lung biopsy of a pulmonary nodule: an analysis of discharge records. Ann Intern Med. 2011 Aug 2;155(3):137–44. Singh N, Aggarwal AN, Gupta D, Behera D, Jindal SK. Unchanging clinico-epidemiological profile of lung cancer in north India over three decades. Cancer Epidemiol. 2010 Feb;34(1):101–4. Rao S, Anthony M, Chowdhury N, Kathrotia R, Mishra M, Naithani M, et al. Molecular characterization of lung carcinomas: A study on diagnostic, predictive, and prognostic markers using immunohistochemical analysis at a tertiary care center in Uttarakhand, India. J Carcinog. 2021;20(1):17. Malik PS, Sharma MC, Mohanti BK, Shukla NK, Deo S, Mohan A, et al. Clinicopathological profile of lung cancer at AIIMS: a changing paradigm in India. Asian Pac J Cancer Prev APJCP. 2013;14(1):489–94. Nair Ck, Mathew A, George P. Lung cancer: Presentation and pattern of care in a cancer center in South India. Indian J Cancer. 2017;54(1):164. Kozielski J, Kaczmarczyk G, Porębska I, Szmygin-Milanowska K, Gołecki M. Lung cancer in patients under the age of 40 years. Współczesna Onkol. 2012;5:413–5. Mousavi SM, Schmid S, Cerny T, Früh M. Lung cancer and smoking trends in the young in Switzerland. Swiss Med Wkly. 2018 Dec 17;148:w14708. Jemal A, Miller KD, Ma J, Siegel RL, Fedewa SA, Islami F, et al. Higher Lung Cancer Incidence in Young Women Than Young Men in the United States. N Engl J Med. 2018 May 24;378(21):1999–2009. Raj Drs. Histopathological And Immunohistochemical Analysis Of Non-Small Cell Lung Carcinoma With Special Emphasis On EGFR Expression. http://repository-tnmgrmu.ac.in/9319/:133. Dey A, Biswas D, Saha SK, Kundu S, Kundu S, Sengupta A. Comparison study of clinicoradiological profile of primary lung cancer cases: an Eastern India experience. Indian J Cancer. 2012 Mar;49(1):89–95. Singh N, Aggarwal AN, Gupta D, Behera D, Jindal SK. Quantified smoking status and non-small cell lung cancer stage at presentation: analysis of a North Indian cohort and a systematic review of literature. J Thorac Dis. 2012 Oct;4(5):474–84. Mohan A, Garg A, Gupta A, Sahu S, Choudhari C, Vashistha V, et al. Clinical profile of lung cancer in North India: A 10-year analysis of 1862 patients from a tertiary care center. Lung India. 2020;37(3):190. Krishnamurthy A, Gadigi V, Sagar T, Vijayalakshmi R, Ranganathan R. The relevance of “Nonsmoking-associated lung cancer” in India: A single-centre experience. Indian J Cancer. 2012;49(1):82. Santos-Martínez MJ, Curull V, Blanco ML, Macià F, Mojal S, Vila J, et al. Lung cancer at a university hospital: epidemiological and histological characteristics of a recent and a historical series. Arch Bronconeumol. 2005 Jun;41(6):307–12. Bhaskarapillai B, Kumar SS, Balasubramanian S. Lung cancer in Malabar Cancer Center in Kerala—a descriptive analysis. Asian Pac J Cancer Prev APJCP. 2012;13(9):4639–43. O’Keeffe LM, Taylor G, Huxley RR, Mitchell P, Woodward M, Peters SAE. Smoking as a risk factor for lung cancer in women and men: a systematic review and meta-analysis. BMJ Open. 2018 Oct;8(10):e021611. Miranda-Filho A, Piñeros M, Bray F. The descriptive epidemiology of lung cancer and tobacco control: global overview 2018. Salud Pública México. 2019 Jun 7;61(3):219. Goldkorn T, Filosto S, Chung S. Lung Injury and Lung Cancer Caused by Cigarette Smoke-Induced Oxidative Stress. Antioxid Redox Signal. 2014 Nov 20;21(15):2149–74. Rawat J, Sindhwani G, Gaur D, Dua R, Saini S. Clinicopathological profile of lung cancer in Uttarakhand. Lung India Off Organ Indian Chest Soc. 2009 Jul;26(3):74–6. Walia R, Jain D, Madan K, Sharma MC, Mathur SR, Mohan A, et al. p40 & thyroid transcription factor-1 immunohistochemistry: A useful panel to characterize NSCLC-NOS. Indian J Med Res. 2017 Jul;146(1):42–8. Bhatti V, Kwatra KS, Puri S, Calton N. Histopathological spectrum and immunohistochemical profile of lung carcinomas: A 9-year study from a tertiary hospital in North India. Int J Appl Basic Med Res. 2019;9(3):169–75. Kumari S, Johri N, Gupta S, Ansari SA, Pandey S, Ansari AK. Study of Histopathological Spectrum and Immunohistochemical Profile of Primary Lung Carcinomas at a Tertiary Care Hospital. Res J Med Sci. 2024;18:496–501. Goyal N, Jindal A, Bagarhatta M, Choudhary M, Aggarwal K. Role of immunohistochemical markers for the histological subtyping of core needle biopsies in cases of lung carcinoma. Int J Sci Res. 2023 Jun;12(6):1–4. Rawat J, Sindhwani G, Gaur D, Dua R, Saini S. Clinicopathological profile of lung cancer in Uttarakhand. Lung India. 2009 Apr;26(2):74–6. Pelosi G, Pasini F, Olsen Stenholm C, Pastorino U, Maisonneuve P, Sonzogni A, et al. p63 immunoreactivity in lung cancer. J Pathol. 2002 Sep;198(1):100–9. Nakamura H, Saji H. Worldwide trend of increasing primary adenocarcinoma of the lung. Surg Today. 2014 Jun;44(6):1004–12. Fatima N, Cohen C, Lawson D, Siddiqui MT. TTF-1 and Napsin A double stain: A useful marker for diagnosing lung adenocarcinoma. Cancer Cytopathol. 2011;119(2):127–33. Righi L, Graziano P, Fornari A, Rossi G, Barbareschi M, Cavazza A, et al. Immunohistochemical subtyping of NSCLC-NOS in FNAC. Cancer. 2011 Aug 1;117(15):3416–23. Chen K, Bai C, Xu J, Zhang X, Lv J, Wang X, et al. Expression of p63 and CK5/6 in early-stage lung SCC. Thorac Cancer. 2015;6(4):418–25. Wang JY, Wang XM, Xu XY, Li SR, Liu XL. Expression of CK5/6, p63, p40, CK7, TTF-1, napsin A, CD56, synaptophysin and chromogranin A in lung carcinoma biopsies. Int J Morphol. 2020;38(2):247–51. Pelosi G, Pasini F, Olsen Stenholm C, Pastorino U, Maisonneuve P, Sonzogni A, et al. p63 immunoreactivity in lung cancer. J Pathol. 2002 Sep;198(1):100–9. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8305530","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":614920632,"identity":"aade2a44-0f75-4f7b-9985-db10cb44b099","order_by":0,"name":"Zainab Ashfaque Ali","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABA0lEQVRIiWNgGAWjYFACxgYQYgay2D9+qABSzMwNRGthY5Y4A9LCSEgLRBcIsDHwtiFxcQH59sNtD37usGPXbe999kByXm00fztQy4+Kbbgt6ElsN+w9k8xsdua4uUHhtuO5Mw4zNjD2nLmNUwszQ2KbBG8bM7PZjTQGCcltx3IbgFqYGdtwa2Hjf9gm+betntns/jMGCd45x3LnE9LCI5HYJs3bdhhoCxubBG9DTe4GQlokJB62ScueOQ70SxqzscSxA7kbgVoO4vOLfH/6M8m3O6qTzY4fY3z4oaYud975wwcf/KjArQUGkqH0YTB5gKB6ILCD0nXEKB4Fo2AUjIIRBgDgOlqAJXvkugAAAABJRU5ErkJggg==","orcid":"","institution":"RNT Medical College","correspondingAuthor":true,"prefix":"","firstName":"Zainab","middleName":"Ashfaque","lastName":"Ali","suffix":""},{"id":614920633,"identity":"8b585b93-6772-4085-b909-6df5864f99d6","order_by":1,"name":"Namita Goyal","email":"","orcid":"","institution":"RNT Medical College","correspondingAuthor":false,"prefix":"","firstName":"Namita","middleName":"","lastName":"Goyal","suffix":""},{"id":614920634,"identity":"ddce2867-3467-4eb1-b96e-f53b00330a2d","order_by":2,"name":"Gunjan bhatia","email":"","orcid":"","institution":"RNT Medical College","correspondingAuthor":false,"prefix":"","firstName":"Gunjan","middleName":"","lastName":"bhatia","suffix":""},{"id":614920635,"identity":"1aa7df80-b3e9-4d4d-9c9c-800d01a7d43c","order_by":3,"name":"Archana dodiyal","email":"","orcid":"","institution":"RNT Medical College","correspondingAuthor":false,"prefix":"","firstName":"Archana","middleName":"","lastName":"dodiyal","suffix":""}],"badges":[],"createdAt":"2025-12-08 09:48:11","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8305530/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8305530/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":105982893,"identity":"678860d3-8a2d-4f6a-9012-f9d65513e121","added_by":"auto","created_at":"2026-04-02 07:06:07","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":865461,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eA: SCC in H \u0026amp; E section (400X),\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eB: CK5/6 cytoplasmic\u003c/strong\u003e \u003cstrong\u003epositivity in SCC IHC (400X)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eC: TTF 1 negative staining in SCC - IHC (400X)\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8305530/v1/c2dc4a29dedcfafe78b0e37d.png"},{"id":106094280,"identity":"989f558e-b19c-4d57-94ec-287e2fb87ff3","added_by":"auto","created_at":"2026-04-03 11:42:02","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1040873,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eA: ADC in H \u0026amp; E section (400X),\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eB: TTF1 nuclear\u003c/strong\u003e \u003cstrong\u003epositivity in ADC IHC (400X)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eC: CK5/6 negative staining in ADC - IHC (400X)\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8305530/v1/656ddb53d5cea47e47aa4b94.png"},{"id":105982895,"identity":"a831a77f-1186-403d-9e7c-50b00572cb7f","added_by":"auto","created_at":"2026-04-02 07:06:07","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1056382,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eA: NSCLC FAV SCC in H \u0026amp; E section, (200X), B: CK5/6 cytoplasmic\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003epositivity in NSCLC FAV SCC- IHC (CK5/6) (200X), C: TTF 1\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003enegative staining in NSCLC FAV SCC - IHC (TTF 1) (200X),\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8305530/v1/a5e1c309cca5b6ee95239098.png"},{"id":106094312,"identity":"45e1abcf-9ca7-48c8-8efb-acb0ae49ab2d","added_by":"auto","created_at":"2026-04-03 11:42:07","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":468296,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eA: NSCLC FAV ADC in H \u0026amp; E section, (200X),\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eB: TTF1 nuclear positivity in NSCLC FAV ADC -IHC (TTF 1) (200X)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eC: CK5/6 negative staining in NSCLC FAV ADC -IHC (CK5/6) (200X)\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8305530/v1/78885f745825043bbf773164.png"},{"id":108566196,"identity":"e01f864a-937c-4c39-932c-1c98947335ef","added_by":"auto","created_at":"2026-05-06 04:41:09","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4000568,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8305530/v1/98846f67-0116-4d8a-a2b7-8590a444274c.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eDiagnostic Utility of CK5/6 and TTF-1 in Subtyping Non-Small Cell Lung Carcinoma: Experience from a Tertiary Care Centre\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eLung cancer, a global public health menace, exerts a profound impact on society. It stands as the most prevalent cancer worldwide, accounting for 1.76\u0026nbsp;million cancer-related deaths annually\u0026sup1;,\u0026sup2;. The disease exhibits a marked gender bias, affecting males nearly twice as often as females\u0026sup3;. In India, lung cancer ranks as the second most common cancer among males and sixth among females, and is the fourth leading cause of cancer-related mortality following breast, cervix, and lip\u0026ndash;oral cavity cancers⁴,⁵.\u003c/p\u003e \u003cp\u003eAccurate diagnosis and classification of lung cancer require small tissue samples, typically obtained via bronchoscopy, percutaneous image-guided techniques, or from metastatic sites. Cell block preparations from malignant pleural effusions also serve as valuable diagnostic tools⁶. However, challenges arise with minute biopsies, making immunohistochemistry (IHC) crucial for histological categorization, forming the foundation for molecular investigations and treatment strategies⁷.\u003c/p\u003e \u003cp\u003eIHC is widely available, cost-effective, and can be performed on small samples, aiding in tumor subtyping and biomarker assessment⁸. NSCLC accounts for about 85% of lung cancers and is further subtyped into adenocarcinoma (ADC) and squamous cell carcinoma (SCC)⁹. Histological evaluation alone can be challenging, hence the utility of IHC markers such as CK5/6 (for SCC) and TTF-1 (for ADC) \u0026sup1;⁰, \u0026sup1;\u0026sup1;. This study assesses the role of these markers in accurately subtyping NSCLC in small biopsies from a tertiary care hospital in Southern Rajasthan.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cp\u003e\u003cstrong\u003eStudy Design and Setting:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis cross-sectional study was conducted in the Department of Pathology, R.N.T. Medical College, Udaipur, over a period of 18 months (October 2023 to April 2025). Ethical approval was obtained from the Institutional Ethics Committee of R.N.T. Medical College, Udaipur (Approval No.: 2024/810). All methods were performed in accordance with the relevant guidelines and regulations, including the Declaration of Helsinki. Written informed consent was obtained from all participants prior to inclusion in the study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSample Size:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSixty-four NSCLC cases diagnosed on histopathology were included.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInclusion Criteria:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026bull; Patients of all ages and both sexes\u003c/p\u003e\n\u003cp\u003e\u0026bull; Adequate clinical and imaging assessment\u003c/p\u003e\n\u003cp\u003e\u0026bull; Specimens obtained via bronchoscopy, image-guided percutaneous biopsy, or cell block preparations\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eExclusion Criteria:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026bull; Benign and infective lung lesions\u003c/p\u003e\n\u003cp\u003e\u0026bull; Secondary (metastatic) lung malignancies\u003c/p\u003e\n\u003cp\u003e\u0026bull; Inadequate biopsies (autolyzed or scant samples)\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eProcedure\u003c/strong\u003e:\u003c/p\u003e\n\u003cp\u003eLung biopsies were fixed in 10% neutral buffered formalin, processed, embedded in paraffin, sectioned at 3\u0026ndash;4 \u0026mu;m, and stained with Hematoxylin \u0026amp; Eosin (H\u0026amp;E). Immunohistochemistry (IHC) was performed using the LEICA BOND MAX Premium system. CK5/6 cytoplasmic positivity in \u0026ge;50% of tumor cells indicated squamous cell carcinoma (SCC), while TTF-1 nuclear positivity in \u0026gt;50% of tumor cells indicated adenocarcinoma (ADC).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatistical Analysis:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData were analysed using SPSS software. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated. A p-value \u0026lt;0.05 was considered statistically significant.\u003c/p\u003e"},{"header":"OBSERVATION AND RESULTS","content":"\u003cp\u003eA total of 64 cases of NSCLCs were analysed in this study. All of them were biopsy specimens, obtained\u0026nbsp;via bronchoscopy, percutaneous methods guided by imaging and cell block preparations.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAge and gender distribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe age of the cases of NSCLC ranged from 23 to 85 years, with the mean age being 62.14 years. The maximum number of cases were in the age group of 61 to 70 years (20 cases, 31.25%).\u003c/p\u003e\n\u003cp\u003eThere was a clear male predominance; out of 64 cases, 50 (78.1%) were males and 14 (21.9%) were females.\u003c/p\u003e\n\u003cp\u003eA comparison of age distribution and gender revealed male predominance across all age groups.\u003c/p\u003e\n\u003cp\u003eAmong the 14 females, the most common age group was 61 to 70 years, followed by 71 to 80 years.\u003c/p\u003e\n\u003cp\u003eAmong the 50 male cases, 39 (78%) were above 50 years, and only 11 (22%) were below 50 years of age (Table 1)\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1: Age and gender distribution\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 91px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAge\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMale\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n=50)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 135px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eFemale\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n=14)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTotal\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n=64)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 91px;\"\u003e\n \u003cp\u003e21-30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 135px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 91px;\"\u003e\n \u003cp\u003e31-40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 135px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 91px;\"\u003e\n \u003cp\u003e41-50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 135px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 91px;\"\u003e\n \u003cp\u003e51-60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 135px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e13\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 91px;\"\u003e\n \u003cp\u003e61-70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 135px;\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e23\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 91px;\"\u003e\n \u003cp\u003e71-80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 135px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 91px;\"\u003e\n \u003cp\u003e81-90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 135px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eTumour site\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThere were more cases in the right lung (38 cases, 59.4%) compared to the left lung (20 cases, 31.2%). In 6 cases (9.4%), the tumor was diagnosed on cell block material, and the exact anatomical location could not be determined.In the right lung, the tumor was located in the upper lobe in 25 cases (65.8%), middle lobe in 4 cases (10.5%), lower lobe in 9 cases (23.7%)In the left lung, the tumor involved the upper lobe in 15 cases (75%), lower lobe in 5 cases (25%).\u003c/p\u003e\n\u003cp\u003e(\u003cstrong\u003eTable 2): Distribution of cases based on laterality and location\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" align=\"\" width=\"387\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eRight lung\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003en=38\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;Left lung\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003en =20\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eCell block\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003en=6\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003eUpper lobe=25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u0026nbsp;upper lobe=15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003eMiddle lobe=4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003elower lobe =5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003eLower lobe= 9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eHistological type of tumour prior to IHC\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAs per the records in the histopathology department, the 64 tumours had been initially typed histologically according to the WHO Classification of Tumours of the Lung, Pleura, Thymus and Heart (4th edition).\u003c/p\u003e\n\u003cp\u003eThe most common histological type of lung carcinoma was squamous cell carcinoma (SCC) \u0026nbsp;(n = 30, 46.9%), followed by adenocarcinoma (ADC) (n = 21, 32.8%) and non-small cell lung carcinoma \u0026ndash; not otherwise specified (NSCLC, NOS) (n = 13, 20.3%).\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 3:\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eHistological types of NSCLCs before using IHC\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" align=\"left\" width=\"548\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 150px;\"\u003e\n \u003cp\u003eSquamous cell carcinoma\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 152px;\"\u003e\n \u003cp\u003eAdenocarcinoma\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003eNon small cell (unclassified)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eTotal\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 150px;\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 152px;\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e64\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eIHC staining pattern in the different types of NSCLCs\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eOn application of immunohistochemical (IHC) stains, a total of 40 cases showed CK5/6 positivity, confirming the diagnosis of squamous cell carcinoma (SCC). Among these, TTF-1 positivity was observed in 3 out of 40 SCC cases (7.5%), but the staining intensity was weak in all three cases. These cases were still classified as SCC due to strong CK5/6 positivity and supportive squamous morphology.-1 positivity in 24 cases,\u003c/p\u003e\n\u003cp\u003eImmunohistochemical (IHC) staining showed TTF-1 positivity in 24 cases, supporting the diagnosis of adenocarcinoma (ADC). TTF-1 alone was positive in 19 cases, while CK5/6 expression was observed in 7 out of 21 cases (33.3%). Among these, five cases showed focal or weak staining, and two cases demonstrated strong positivity. Despite CK5/6 expression, these cases were classified as adenocarcinoma based on their predominant glandular morphology and strong TTF-1 immunoreactivity, rather than squamous differentiation.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eHistological type of tumour after IHC\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe tumours were reclassified after immunohistochemistry with TTF 1 and CK5/6 . Those tumours which showed nuclear positivity for TTF 1, negative staining for CK5/6 were typed as adenocarcinomas. (Figure 2, A-D) The histological type of majority of the cases was squamous cell carcinoma 40 cases. The tumours which had strong cytoplasmic and membranous positivity for CK5/6 and negative staining for TTF 1 were classified as Squamous cell carcinoma (Figure 1, A-D). The NSCLC were recategorized as follows:\u003c/p\u003e\n\u003cul type=\"disc\"\u003e\n \u003cli\u003eThose with a Hand E diagnosis of squamous cell carcinoma, but IHC staining positive for TTF 1, were grouped as NSCLC favouring adenocarcinoma (Figure 2A- D).\u003c/li\u003e\n \u003cli\u003eThose with a Hand E diagnosis of adenocarcinoma, but IHC staining positive for CK5/6 \u0026nbsp;and showing negative staining for TTF1 were grouped as NSCLC favouring squamous cell carcinoma (Figure 1 A-D).\u003c/li\u003e\n \u003cli\u003e13 H and E diagnosed NSCLC NOS were recategorized as 8 squamous cell carcinoma and 5 cases of adenocarcinoma based on their positive staining for CK5/6 and TTF1 respectively.\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eThe frequency distribution of the histological type of NSCLC after IHC is given in (Table5)\u003cstrong\u003e\u0026nbsp;\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 5 : Histological type of tumour after IHC\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 200px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eHistological type after IHC\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 200px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNo. of cases\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 200px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePercentage\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 200px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAdenocarcinoma\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 200px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e19\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 200px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e29.68%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 200px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNSCLC favouring adenocarcinoma\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 200px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e5\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 200px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e7.81%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 200px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSquamous cell carcinoma\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 200px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e32\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 200px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e50%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 200px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNSCLC favouring squamous cell carcinoma\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 200px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e8\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 200px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e12.5%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 200px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTotal no. of cases\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 200px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e64\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 200px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e100%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eSquamous cell carcinoma remained the commonest type of NSCLC after IHC. The number of cases increased (from 30 to 40) while those of adenocarcinoma increased from 21to 24 cases out of a total of 64 cases of NSCLCs.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 6: Significance of adding immunohistochemistry in the diagnosis of non-small cell lung cancer (NSCLC)\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e(n=64)\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 144px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTumour typing based on HPE diagnosis\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 150px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMorphological diagnosis (n=64) (%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 143px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAfter using IHC (CK5/6 and, TTF 1)\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003en (%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 164px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSubtype characterization\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 144px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eADC\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 150px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e21 (32.8%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 143px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e24 (37.5%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 164px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eIncrement by\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e14.29%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 144px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSCC\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 150px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e30 (46.88%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 143px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e40 (62.5%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 164px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eIncrement by\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e33.33%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 144px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNSCLC-NOS\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 150px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e13 (20.3%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 143px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e-\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 164px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eComplete\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003ereduction\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 7: Performance of individual markers TTF 1 and ck5/6 in IHC proven adenocarcinomas and NSCLC favouring adenocarcinoma\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSensitivity\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 114px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSpecificity\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 103px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePPV\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNPV\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 82px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eP value\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eCK5/6\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e79.2%\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 114px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e95%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 103px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e90.5%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e88.4%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 82px;\"\u003e\n \u003cp\u003e\u0026lt;0.0001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTTF1\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e75.0%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 114px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e100%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 103px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e100%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e70.6%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 82px;\"\u003e\n \u003cp\u003e\u0026lt;0.0001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eUsing morphological diagnosis as the screening test and IHC as the gold standard, the analysis revealed the following:\u003c/p\u003e\n\u003cul type=\"disc\"\u003e\n \u003cli\u003eCK5/6 exhibited a sensitivity of 79.2%, specificity of 95.0%, positive predictive value (PPV) of 90.5%, and negative predictive value (NPV) of 88.4%.\u003c/li\u003e\n \u003cli\u003eTTF-1 showed a sensitivity of 75.0%, specificity of 100%, PPV of 100%, and NPV of 70.6%.The statistical association for both markers was highly significant with p-values \u0026lt; 0.0001, reinforcing their diagnostic utility in differentiating adenocarcinoma and squamous cell carcinoma in NSCLC.\u003c/li\u003e\n\u003c/ul\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eLung cancer continues to be a major global health concern due to its high mortality rate, underscoring the importance of accurate tumor classification (12). Since the WHO 2015 update, and more definitively in the WHO Classification of Thoracic Tumours, 5th edition (2021), histological subtyping using immunohistochemistry (IHC) has become mandatory in biopsy reporting to ensure appropriate treatment selection. In this context, the present study aimed to reclassify NSCLC cases initially diagnosed on morphology alone using the updated WHO guidelines.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn our study, the age of patients with NSCLC ranged from 23 to 85 years, with a mean age of 62.14 years. Similar findings were documented by Singh et al. (mean age 58.1 years) and Rao et al. (range 35\u0026ndash;90 years, mean 58.4 years), both highlighting the higher prevalence of NSCLC in elderly males (12,15). The peak incidence in our cohort occurred in the 61\u0026ndash;70-year age group (35.93%), consistent with earlier reports by Nair CK et al. and Malik et al. (16,17).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSquamous cell carcinoma (SCC) cases in our study ranged from 39 to 87 years (mean 51.6 years), comparable to data from Coimbatore, where the majority of SCC cases were between 61 and 70 years, with a mean age of 65.5 years (21). Adenocarcinoma (ADC) cases ranged from 23 to 78 years (mean 44.4 years), slightly younger than reported in Western literature, where ADC frequently presents even below 40 years of age (18\u0026ndash;20).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eA clear male predominance was noted, with a male-to-female ratio of 3.57:1, in agreement with several Indian studies summarized in Table 18. Smoking remains strongly associated with SCC, as demonstrated by landmark studies from Krishnamurthy et al. (25) and Santos-Mart\u0026iacute;nez et al. (26), which reported a higher incidence of SCC among male smokers. In the present study, all IHC-proven SCC cases occurred in males, aligning with established evidence relating smoking to SCC pathogenesis (27\u0026ndash;29).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAmong the 24 adenocarcinoma cases, 60% were males and 40% females, similar to previous findings (21). When stratified by gender, SCC predominated in males (57.44%), whereas ADC was slightly more common among females (54.54%).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eRegarding tumor location, our study showed a slight predominance of right-sided lesions, with the upper lobe being the most commonly involved. Similar observations have been made by Kumar SB et al. and Rawat J et al. (30,31). Studies from AIIMS, New Delhi, have also highlighted the upper lobe as a frequent site of involvement (24). In our cohort, ADCs were predominantly located in the upper lobe, while SCCs more frequently involved the lower lobe.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eBefore IHC, 46.88% of cases were diagnosed as SCC, 32.8% as ADC, and 20.3% as NSCLC-NOS. After applying the recommended IHC markers (CK5/6 and TTF-1), all 13 NSCLC-NOS cases were reclassified\u0026mdash;eight as SCC and five as ADC\u0026mdash;completely eliminating the NSCLC-NOS category. This resulted in a final distribution of 62.5% SCC and 37.5% ADC, corresponding to an increase of 33.33% in SCC and 14.29% in ADC diagnoses after IHC. This improvement aligns with previous studies that have demonstrated the significant impact of IHC in reducing NSCLC-NOS diagnoses (32).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThese results are comparable to earlier reports (Table 19). Globally and within India, SCC has historically been the predominant NSCLC subtype, as noted in studies from Ahmedabad, Bareilly, Jaipur, and Uttarakhand (33\u0026ndash;36). Our study also reported a higher proportion of SCC (62.5%), consistent with similar regional findings.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAlthough recent literature indicates a shift toward increased detection of ADC since 2012 (38), particularly in Western populations, SCC continues to predominate in many Indian cohorts. This difference is likely attributable to regional variations in smoking patterns and environmental exposures. The introduction of sensitive markers such as TTF-1 for ADC and CK5/6 for SCC has further improved diagnostic accuracy, supporting the WHO 2021 recommendations advocating the use of a limited but specific IHC panel (12).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFor statistical purposes, ADC and NSCLC favoring ADC were considered together as adenocarcinoma, while SCC and NSCLC favoring SCC were grouped under squamous cell carcinoma. On initial H\u0026amp;E evaluation, 43 of 64 cases (67.19%) were correctly classified, while 21 cases (32.81%) required reclassification after IHC. Among the 21 histologically diagnosed ADC cases, 13 retained their diagnosis, 2 were reassigned as NSCLC favoring SCC, and 5 of the NSCLC-NOS cases were reclassified as ADC, yielding a final total of 24 ADC cases (37.5%). Similarly, eight NSCLC-NOS cases and two ADC cases were reclassified as SCC, resulting in a total of 40 SCC cases (62.5%) (P = 0.000). These findings parallel those from AIIMS Delhi (Ritika W et al.) and studies by Loo et al., Walia et al., and Pelosi et al., all of which reported significant reclassification of NSCLC-NOS following IHC (32,43).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eEvaluation of immunohistochemical marker expression demonstrated CK5/6 positivity in 62.5% of cases and TTF-1 positivity in 24 cases. Among the initially diagnosed ADC cases, 5 showed both TTF-1 positivity and weak CK5/6 expression, while 13 demonstrated strong TTF-1 positivity alone. One case with strong CK5/6 expression was reclassified as NSCLC favoring SCC. A similar predominance of CK5/6 expression was reported by Shweta et al., where 40 of 58 cases showed positivity (33).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn our study, CK5/6 demonstrated a sensitivity of 75%, specificity of 100%, PPV of 100%, and NPV of 64.3% for identifying SCC. TTF-1 exhibited a sensitivity of 72.2%, specificity of 95%, PPV of 86.7%, and NPV of 88.4%. These values align well with previous studies, where TTF-1 sensitivity and specificity ranged between 75% and over 95% (13,39 ,40). Similar trends for CK5/6 have been reported by Keneng Chen et al. (sensitivity 78.9%, specificity 97.7%) (41) and Wang et al. (2020) (sensitivity 77.05%, specificity 96.44%) (42).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAmong the histologic ADC cases, 2 of 21 (9.52%) showed CK5/6 positivity and were reclassified as SCC, while the remaining 19 (90.47%) cases demonstrated TTF-1 uptake and were categorized as ADC. The higher specificity of CK5/6 compared to its sensitivity parallels findings from earlier studies and underscores its utility as a reliable marker for SCC.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eDr. Zainab Ashfaque Ali was responsible for the conception and design of the study, collection of data, analysis and interpretation of results, and preparation of all tables, figures, and statistical outputs. Dr. Zainab Ashfaq Ali also wrote the primary draft of the manuscript and coordinated the overall research work.Dr. Namita Goyal contributed to manuscript preparation, provided critical academic input, and supervised the study with important intellectual guidance and revisions.Dr. Gunjan Bhatia actively assisted in data analysis, verification of results, and preparation of tables and figures, and contributed to the technical refinement of the study.Dr. Archana Dodiyal assisted in data compilation and supported the preparation of the research work.All authors critically reviewed the manuscript and approved the final version.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eAll data generated and analysed during the current study are included in this article and its related information files. The de-identified raw dataset (Master Chart) used for the analyses is available\u0026nbsp;in related information files.\u003c/p\u003e\u003cp\u003eThe Authors received \u003cstrong\u003eNO FUNDING\u003c/strong\u003e for this work\u0026quot;\u003c/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eBray F, Ferlay J, Soerjomataram I, Siegel RL, Torre LA, Jemal A. Global cancer statistics 2018: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA Cancer J Clin. 2018;68(6):394\u0026ndash;424.\u003c/li\u003e\n \u003cli\u003eSung H, Ferlay J, Siegel RL, Laversanne M, Soerjomataram I, Jemal A, et al. Global cancer statistics 2020: GLOBOCAN estimates of incidence and mortality worldwide. CA Cancer J Clin. 2021;71(3):209\u0026ndash;49.\u003c/li\u003e\n \u003cli\u003eNCRP (National Cancer Registry Programme), ICMR. Report of National Cancer Registry Programme 2020. Bengaluru: ICMR-NCDIR; 2020.\u003c/li\u003e\n \u003cli\u003eVarghese C, Sebastian P. Lung cancer in India: current status and future perspectives. Curr Opin Pulm Med. 2022;28(4):250\u0026ndash;7.\u003c/li\u003e\n \u003cli\u003eTravis WD, Brambilla E, Nicholson AG, Yatabe Y, Austin JHM, Beasley MB, et al. The 2021 WHO classification of lung tumors. J Thorac Oncol. 2021;16(9):933\u0026ndash;47.\u003c/li\u003e\n \u003cli\u003eTravis WD, Brambilla E, Noguchi M, Nicholson AG, Geisinger KR, Yatabe Y, et al. Diagnosis of lung cancer in small biopsies and cytology: implications of the 2015 WHO classification. Ann Oncol. 2015;26(8):1207\u0026ndash;15.\u003c/li\u003e\n \u003cli\u003eMukhopadhyay S, Katzenstein AL. Subtyping of non\u0026ndash;small cell lung carcinoma: a practical approach for small biopsy specimens. Arch Pathol Lab Med. 2009;133(7):1089\u0026ndash;98.\u003c/li\u003e\n \u003cli\u003eTurner BM, Cagle PT, Sainz IM, Zhai QJ, Pryzwansky KB, Dacic S. CK5/6 and p63 are complementary in the diagnosis of pulmonary squamous cell carcinoma. Am J Surg Pathol. 2012;36(5):634\u0026ndash;41.\u003c/li\u003e\n \u003cli\u003eTacha D, Zhou D, Cheng L. TTF-1 monoclonal antibodies: clone dependence and high sensitivity/specificity for lung adenocarcinoma. Appl Immunohistochem Mol Morphol. 2011;19(2):115\u0026ndash;9.\u003c/li\u003e\n \u003cli\u003eMoreira AL, Mukhopadhyay S, Allen TC, Beasley MB, Borczuk AC, Chen G, et al. AAIHDP recommendations for optimal pathologic evaluation of lung cancer biopsy specimens. Arch Pathol Lab Med. 2020;144(3):284\u0026ndash;99.\u003c/li\u003e\n \u003cli\u003eYatabe Y, Kerr KM, Utomo A, Rajadurai P, Du X, Chou T-Y, et al. EGFR mutation testing practices in lung cancer: current status in Asia. J Thorac Oncol. 2015;10(3):412\u0026ndash;6.\u003c/li\u003e\n \u003cli\u003eOrganisation mondiale de la sant\u0026eacute;, Centre international de recherch\u0026eacute; sur le cancer, editors. Thoracic tumours. 5th ed. Lyon: International agency for research on cancer; 2021. (World health organization classification of tumours).\u003c/li\u003e\n \u003cli\u003eWiener RS, Schwartz LM, Woloshin S, Welch HG. Population-based risk for complications after transthoracic needle lung biopsy of a pulmonary nodule: an analysis of discharge records. Ann Intern Med. 2011 Aug 2;155(3):137\u0026ndash;44.\u003c/li\u003e\n \u003cli\u003eSingh N, Aggarwal AN, Gupta D, Behera D, Jindal SK. Unchanging clinico-epidemiological profile of lung cancer in north India over three decades. Cancer Epidemiol. 2010 Feb;34(1):101\u0026ndash;4.\u003c/li\u003e\n \u003cli\u003eRao S, Anthony M, Chowdhury N, Kathrotia R, Mishra M, Naithani M, et al. Molecular characterization of lung carcinomas: A study on diagnostic, predictive, and prognostic markers using immunohistochemical analysis at a tertiary care center in Uttarakhand, India. J Carcinog. 2021;20(1):17.\u003c/li\u003e\n \u003cli\u003eMalik PS, Sharma MC, Mohanti BK, Shukla NK, Deo S, Mohan A, et al. Clinicopathological profile of lung cancer at AIIMS: a changing paradigm in India. Asian Pac J Cancer Prev APJCP. 2013;14(1):489\u0026ndash;94.\u003c/li\u003e\n \u003cli\u003eNair Ck, Mathew A, George P. Lung cancer: Presentation and pattern of care in a cancer center in South India. Indian J Cancer. 2017;54(1):164.\u003c/li\u003e\n \u003cli\u003eKozielski J, Kaczmarczyk G, Porębska I, Szmygin-Milanowska K, Gołecki M. Lung cancer in patients under the age of 40 years. Wsp\u0026oacute;łczesna Onkol. 2012;5:413\u0026ndash;5.\u003c/li\u003e\n \u003cli\u003eMousavi SM, Schmid S, Cerny T, Fr\u0026uuml;h M. Lung cancer and smoking trends in the young in Switzerland. Swiss Med Wkly. 2018 Dec 17;148:w14708.\u003c/li\u003e\n \u003cli\u003eJemal A, Miller KD, Ma J, Siegel RL, Fedewa SA, Islami F, et al. Higher Lung Cancer Incidence in Young Women Than Young Men in the United States. N Engl J Med. 2018 May 24;378(21):1999\u0026ndash;2009.\u003c/li\u003e\n \u003cli\u003eRaj Drs. Histopathological And Immunohistochemical Analysis Of Non-Small Cell Lung Carcinoma With Special Emphasis On EGFR Expression. http://repository-tnmgrmu.ac.in/9319/:133.\u003c/li\u003e\n \u003cli\u003eDey A, Biswas D, Saha SK, Kundu S, Kundu S, Sengupta A. Comparison study of clinicoradiological profile of primary lung cancer cases: an Eastern India experience. Indian J Cancer. 2012 Mar;49(1):89\u0026ndash;95.\u003c/li\u003e\n \u003cli\u003eSingh N, Aggarwal AN, Gupta D, Behera D, Jindal SK. Quantified smoking status and non-small cell lung cancer stage at presentation: analysis of a North Indian cohort and a systematic review of literature. J Thorac Dis. 2012 Oct;4(5):474\u0026ndash;84.\u003c/li\u003e\n \u003cli\u003eMohan A, Garg A, Gupta A, Sahu S, Choudhari C, Vashistha V, et al. Clinical profile of lung cancer in North India: A 10-year analysis of 1862 patients from a tertiary care center. Lung India. 2020;37(3):190.\u003c/li\u003e\n \u003cli\u003eKrishnamurthy A, Gadigi V, Sagar T, Vijayalakshmi R, Ranganathan R. The relevance of \u0026ldquo;Nonsmoking-associated lung cancer\u0026rdquo; in India: A single-centre experience. Indian J Cancer. 2012;49(1):82.\u003c/li\u003e\n \u003cli\u003eSantos-Mart\u0026iacute;nez MJ, Curull V, Blanco ML, Maci\u0026agrave; F, Mojal S, Vila J, et al. Lung cancer at a university hospital: epidemiological and histological characteristics of a recent and a historical series. Arch Bronconeumol. 2005 Jun;41(6):307\u0026ndash;12.\u003c/li\u003e\n \u003cli\u003eBhaskarapillai B, Kumar SS, Balasubramanian S. Lung cancer in Malabar Cancer Center in Kerala\u0026mdash;a descriptive analysis. Asian Pac J Cancer Prev APJCP. 2012;13(9):4639\u0026ndash;43.\u003c/li\u003e\n \u003cli\u003eO\u0026rsquo;Keeffe LM, Taylor G, Huxley RR, Mitchell P, Woodward M, Peters SAE. Smoking as a risk factor for lung cancer in women and men: a systematic review and meta-analysis. BMJ Open. 2018 Oct;8(10):e021611.\u003c/li\u003e\n \u003cli\u003eMiranda-Filho A, Pi\u0026ntilde;eros M, Bray F. The descriptive epidemiology of lung cancer and tobacco control: global overview 2018. Salud P\u0026uacute;blica M\u0026eacute;xico. 2019 Jun 7;61(3):219.\u003c/li\u003e\n \u003cli\u003eGoldkorn T, Filosto S, Chung S. Lung Injury and Lung Cancer Caused by Cigarette Smoke-Induced Oxidative Stress. Antioxid Redox Signal. 2014 Nov 20;21(15):2149\u0026ndash;74.\u003c/li\u003e\n \u003cli\u003eRawat J, Sindhwani G, Gaur D, Dua R, Saini S. Clinicopathological profile of lung cancer in Uttarakhand. Lung India Off Organ Indian Chest Soc. 2009 Jul;26(3):74\u0026ndash;6.\u003c/li\u003e\n \u003cli\u003eWalia R, Jain D, Madan K, Sharma MC, Mathur SR, Mohan A, et al. p40 \u0026amp; thyroid transcription factor-1 immunohistochemistry: A useful panel to characterize NSCLC-NOS. Indian J Med Res. 2017 Jul;146(1):42\u0026ndash;8.\u003c/li\u003e\n \u003cli\u003eBhatti V, Kwatra KS, Puri S, Calton N. Histopathological spectrum and immunohistochemical profile of lung carcinomas: A 9-year study from a tertiary hospital in North India. Int J Appl Basic Med Res. 2019;9(3):169\u0026ndash;75.\u003c/li\u003e\n \u003cli\u003eKumari S, Johri N, Gupta S, Ansari SA, Pandey S, Ansari AK. Study of Histopathological Spectrum and Immunohistochemical Profile of Primary Lung Carcinomas at a Tertiary Care Hospital. Res J Med Sci. 2024;18:496\u0026ndash;501.\u003c/li\u003e\n \u003cli\u003eGoyal N, Jindal A, Bagarhatta M, Choudhary M, Aggarwal K. Role of immunohistochemical markers for the histological subtyping of core needle biopsies in cases of lung carcinoma. Int J Sci Res. 2023 Jun;12(6):1\u0026ndash;4.\u003c/li\u003e\n \u003cli\u003eRawat J, Sindhwani G, Gaur D, Dua R, Saini S. Clinicopathological profile of lung cancer in Uttarakhand. Lung India. 2009 Apr;26(2):74\u0026ndash;6.\u003c/li\u003e\n \u003cli\u003ePelosi G, Pasini F, Olsen Stenholm C, Pastorino U, Maisonneuve P, Sonzogni A, et al. p63 immunoreactivity in lung cancer. J Pathol. 2002 Sep;198(1):100\u0026ndash;9.\u003c/li\u003e\n \u003cli\u003eNakamura H, Saji H. Worldwide trend of increasing primary adenocarcinoma of the lung. Surg Today. 2014 Jun;44(6):1004\u0026ndash;12.\u003c/li\u003e\n \u003cli\u003eFatima N, Cohen C, Lawson D, Siddiqui MT. TTF-1 and Napsin A double stain: A useful marker for diagnosing lung adenocarcinoma. Cancer Cytopathol. 2011;119(2):127\u0026ndash;33.\u003c/li\u003e\n \u003cli\u003eRighi L, Graziano P, Fornari A, Rossi G, Barbareschi M, Cavazza A, et al. Immunohistochemical subtyping of NSCLC-NOS in FNAC. Cancer. 2011 Aug 1;117(15):3416\u0026ndash;23.\u003c/li\u003e\n \u003cli\u003eChen K, Bai C, Xu J, Zhang X, Lv J, Wang X, et al. Expression of p63 and CK5/6 in early-stage lung SCC. Thorac Cancer. 2015;6(4):418\u0026ndash;25.\u003c/li\u003e\n \u003cli\u003eWang JY, Wang XM, Xu XY, Li SR, Liu XL. Expression of CK5/6, p63, p40, CK7, TTF-1, napsin A, CD56, synaptophysin and chromogranin A in lung carcinoma biopsies. Int J Morphol. 2020;38(2):247\u0026ndash;51.\u003c/li\u003e\n \u003cli\u003ePelosi G, Pasini F, Olsen Stenholm C, Pastorino U, Maisonneuve P, Sonzogni A, et al. p63 immunoreactivity in lung cancer. J Pathol. 2002 Sep;198(1):100\u0026ndash;9.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Non-small cell lung carcinoma, CK5/6, TTF-1, Immunohistochemistry, Histopathology","lastPublishedDoi":"10.21203/rs.3.rs-8305530/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8305530/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eIntroduction:\u003c/h2\u003e \u003cp\u003eAccurate subtyping of non-small cell lung carcinoma (NSCLC) is essential for therapeutic decision-making. Small biopsies often present diagnostic challenges, making immunohistochemistry (IHC) crucial. This study evaluated the histopathological spectrum and diagnostic utility of CK5/6 and thyroid transcription factor-1 (TTF-1) in NSCLC cases.\u003c/p\u003e\u003ch2\u003eMaterials and Methods:\u003c/h2\u003e \u003cp\u003eThis cross-sectional study was conducted over 18 months in the Department of Pathology, RNT medical college. Sixty-four NSCLC cases diagnosed on histopathology were included. Specimens were processed routinely, stained with Hematoxylin \u0026amp; Eosin, and subjected to IHC for CK5/6 and TTF-1. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated.\u003c/p\u003e\u003ch2\u003eResults:\u003c/h2\u003e \u003cp\u003eBefore IHC, SCC, ADC, and NSCLC\u0026ndash;NOS accounted for 46.88%, 32.8%, and 20.3% of cases, respectively. After IHC, SCC increased to 62.5%, ADC to 37.5%, and NSCLC\u0026ndash;NOS reduced to 0%. CK5/6 showed sensitivity 79.2%, specificity 95%, PPV 90.5%, NPV 88.4% (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). TTF-1 showed sensitivity 75%, specificity 100%, PPV 100%, NPV 70.6% (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001).\u003c/p\u003e\u003ch2\u003eConclusion:\u003c/h2\u003e \u003cp\u003eThe combined use of CK5/6 and TTF-1 significantly improves NSCLC subclassification, eliminating the NSCLC\u0026ndash;NOS category. Routine application in small biopsies can enhance diagnostic accuracy and guide therapy.\u003c/p\u003e","manuscriptTitle":"Diagnostic Utility of CK5/6 and TTF-1 in Subtyping Non-Small Cell Lung Carcinoma: Experience from a Tertiary Care Centre","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-02 07:06:03","doi":"10.21203/rs.3.rs-8305530/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f6b60691-5581-448b-b73f-f66ba53921ad","owner":[],"postedDate":"April 2nd, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":65563749,"name":"Biological sciences/Cancer"},{"id":65563750,"name":"Health sciences/Diseases"},{"id":65563751,"name":"Health sciences/Oncology"}],"tags":[],"updatedAt":"2026-05-06T04:40:21+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-02 07:06:03","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8305530","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8305530","identity":"rs-8305530","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}