Sarcoidosis with Intraabdominal Involvement Mimicking Lymphoma: A Diagnostic Pitfall

Sarcoidosis with Intraabdominal Involvement Mimicking Lymphoma: A Diagnostic Pitfall | 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 Case Report Sarcoidosis with Intraabdominal Involvement Mimicking Lymphoma: A Diagnostic Pitfall Nusaiba Al Maqrashi, Masoud Kashoub, Fathiya Al-Rahbi, Hawra Al Lawati, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7618197/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 12 You are reading this latest preprint version Abstract Background Sarcoidosis is a multisystem granulomatous disease with various manifestations. While pulmonary involvement is most common, intra-abdominal sarcoidosis is rare and often mimics malignancy, leading to misdiagnosis and delayed therapy. Case Presentation: We describe an elderly woman who was initially misdiagnosed with lymphoma at another center based on imaging demonstrating intra-abdominal lymphadenopathy and ascites and histopathological findings. She was started on corticosteroids in preparation for chemotherapy. Patient develooped recurrent ascites requring repeated paracentesis. However, reevaluation at our institution revealed non-caseating granulomas without malignant cells on omental biopsies. Additional investigations confirmed bilateral hilar and mediastinal lymphadenopathy, and comprehensive microbiological workup excluded infectious causes, including tuberculosis. Following a course of corticosteroid therapy, the patient experienced complete resolution of symptoms and near-complete radiologic improvement on follow-up PET imaging. Conclusion This case underscores the diagnostic challenges posed by sarcoidosis with atypical intra-abdominal involvement. Careful histological evaluation is critical to avoid misdiagnosis and inappropriate treatment. Familiarity with such uncommon clinical manifestations is critical for the accurate differentiation of sarcoidosis from other differential diagnosis, notably lymphoma, thereby ensuring timely initiation of effective therapy. Lymphoma Recurrent Ascites Granuloma Noncaseating Sarcoidosis Lymphadenopathy Figures Figure 1 Figure 2 Introduction Sarcoidosis is a systemic inflammatory disease characterized by the formation of non-caseating granulomas in multiple organs, most commonly the lungs and thoracic lymph nodes. 1 , 2 While pulmonary involvement is the hallmark feature, sarcoidosis can manifest with a wide spectrum of extrapulmonary presentations that often pose diagnostic challenges. The incidence of sarcoidosis varies geographically, with higher prevalence observed among African Americans and Scandinavian population, and most patients present between 25 and 50 years of age. 2 However, sarcoidosis in elderly patients is less common and may present atypically, sometimes mimicking malignancy or other systemic diseases. Abdominal sarcoidosis, including peritoneal involvement, is uncommon and may present with nonspecific findings such as ascites or intra-abdominal lymphadenopathy, which can easily be mistaken for other conditions such as metastatic cancer and lymphoproliferative disease. 3 , 4 In such scenarios, histopathological confirmation is essential for accurate diagnosis, as radiologic findings alone are often insufficient to distinguish it from malignancy or infectious etiologies such as tuberculosis. Here, we present a case of an elderly woman whose clinical presentation initially suggested malignancy. However, further evaluation at our center, including comprehensive tissue analysis, revealed an alternative etiology. The patient's clinical course and subsequent response to treatment emphasize the critical importance of re-evaluating cases with atypical clinical presentations and maintaining a broad differential diagnosis when initial findings are incongruent. Case Presentation We present the case of a 61-year-old woman who was first seen at our institution in November 2023 in the hematology/lymphoma clinic for further evaluation of a presumptive diagnosis of peripheral T-cell lymphoma (PTCL-NOS). She had a 1-year history of vague epigastric pain, reduced appetite, and intermittent abdominal distension, along with intermittent low-grade fever, occasional nonproductive cough, and significant back pain. Six months prior, she had developed progressive abdominal swelling and was found to have moderate-to-large ascites and generalized lymphadenopathy. A Positron Emission Tomography (PET) scan performed abroad in October 2023 showed a heterogeneous nodular lesion with mild Fluorodeoxyglucose (FDG) uptake in the pancreatic body, along with extensive lymphadenopathy involving periportal, portocaval, celiac, paraaortic, mesenteric, and mediastinal lymph nodes [images not shown]. Mediastinal, liver, and peripancreatic lymph node biopsies performed abroad had reportedly shown findings suspicious for PTCL-NOS, with a Ki-67 index of 10–15% and pending CD30 immunostaining. She was empirically started on corticosteroids—completed only a few days of therapy—before being evaluated at our center, in preparation for chemotherapy. However, at our center, the biopsy slides were reviewed by pathologists and found to be inconsistent with lymphoma. A repeat PET/CT scan in November 2023 demonstrated FDG-avid lymphadenopathy involving both the mediastinum and abdomen, with a subcarinal lymph node showing a maximum standardized uptake value (SUV max) of 7.3 (Fig. 1A1–A2). Concurrent Computed Tomography (CT) imaging also revealed reaccumulation of ascitic fluid and hepatomegaly (Fig. 1 B). Given the discrepancy between imaging findings and histopathological results inconsistent with lymphoma, a comprehensive re-evaluation was undertaken. Ascitic fluid analysis, done several times and repeatedly revealed an exudative profile with Serum-Ascites Albumin Gradient(SAAG) < 11 g/L, with a fluid albumin of 34 g/L, normal LDH, and lymphocytic predominance. Flow cytometry demonstrated mature T-cell predominance with an increased CD4:CD8 ratio and partial CD7 loss, but no evidence of clonal T-, B-, or Natural Killer (NK)-cell populations. An extensive infectious-disease evaluation—including analyses of ascitic fluid and lymph-node tissue with acid-fast bacilli (AFB) staining, Mycobacterium tuberculosis GeneXpert testing and cultures, fungal cultures, and Q-fever serologies—was negative or non-contributory. Serum Angiotensin-Converting Enzyme (ACE) level was 44 U/L, which was within the normal laboratory reference range (12–68 U/L). In December 2023, she underwent endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) of mediastinal lymph nodes, which revealed epithelioid non-caseating granulomas. No malignant cells were seen, and AFB stain, Gene Xpert, and TB cultures were all negative [Not shown]. A laparoscopic omental biopsy performed in April 2024 demonstrated fibroadipose tissue containing scattered nodules of poorly formed, non-caseating granulomas composed of epithelioid histiocytes surrounded by a thin rim of lymphocytes (Fig. 2 a–b). No atypia or malignant features were observed. Special stains including Periodic Acid–Schiff (PAS), Grocott's Methenamine Silver (GMS), and Ziehl-Neelsen (ZN) were negative for microorganisms (Fig. 2 a–b). A summary of all diagnostic investigations, key differential diagnoses, and the rationale for exclusion is presented in Table 1 . Following multidisciplinary discussion and reasonable exclusion of infectious etiologies, she was started on oral prednisolone 20 mg once daily. After six weeks of therapy, her abdominal distension resolved and her overall well-being improved, with no further need for paracentesis.A follow-up PET/CT scan in May 2024 demonstrated stable mediastinal lymph nodes with no new FDG-avid lesions (Fig. 1 , C1– 2 ) and absence of ascites. Table 1 Summary of Diagnostic Work-up and Differential Diagnosis Category / Test Findings Differential Diagnoses Considered Reason Ruled Out Imaging PET/CT: FDG-avid mediastinal & abdominal lymphadenopathy; ascites; mild pancreatic FDG uptake Lymphoma, peritoneal carcinomatosis, tuberculosis Imaging alone non-specific; histology negative for malignancy or infection Ascitic Fluid Analysis Exudative; SAAG < 11 g/L; albumin 34 g/L; normal LDH; lymphocyte-predominant TB peritonitis, peritoneal carcinomatosis, lymphoma Cytology: no malignant cells; repeated cultures AFB/fungal negative Flow Cytometry (Ascitic fluid) Mature T-cell predominance, ↑CD4:CD8, partial CD7 loss; no clonal T-, B- or NK-cell populations Peripheral T-cell lymphoma No clonal population or atypical lymphoid cells Pathology – Prior External LN/Liver Biopsies Initially “suspicious for PTCL-NOS” Lymphoma Review at SQUH: no malignancy features, only granulomatous inflammation EBUS-TBNA (Mediastinal lymph node) Epithelioid non-caseating granulomas; no malignant cells Lymphoma, TB, fungal infection Special stains/cultures negative Omental Biopsy Poorly formed non-caseating granulomas; PAS, GMS, Ziehl–Neelsen stains negative Lymphoma, TB, fungal, IgG4-related disease No atypia or microorganisms; histology classic for sarcoidosis Microbiologic Studies AFB stain, TB GeneXpert, TB cultures: negative; fungal cultures: negative; Q-fever serology: negative Tuberculosis, fungal peritonitis, Q-fever All negative Laboratory ACE 44 U/L (normal); routine labs unremarkable — ACE not elevated but normal ACE does not exclude sarcoidosis Clinical Course Excellent response to corticosteroids; radiologic resolution Confirms inflammatory granulomatous etiology Malignancy or infection unlikely with steroid-only resolution Table 1 Comprehensive Diagnostic Work-up and Differential Diagnoses in a Patient with Intra-abdominal Sarcoidosis Summary of all investigations performed, the key differential diagnoses considered (including lymphoma, tuberculosis, peritoneal carcinomatosis, fungal infections, IgG4-related disease, and Q-fever), and the rationale for exclusion of each condition, leading to the final diagnosis of systemic sarcoidosis with intra-abdominal involvement. The corticosteroid regimen was continued with gradual tapering over 6–7 months. The patient remained clinically stable, and a repeat PET/CT scan in June 2025 demonstrated marked interval reduction in FDG uptake (SUV declined from 4.0 to 2.3) with no new sites of disease activity (Fig. 1D1–D2), consistent with a complete metabolic response. Given the consistent histologic findings of non-caseating granulomas across multiple biopsy sites, the exclusion of malignant or infectious causes, and the excellent clinical and radiologic response to corticosteroids, a diagnosis of systemic sarcoidosis with intra-abdominal and mediastinal involvement was established. Although a longer course of corticosteroid therapy was recommended, the patient declined continuation because of concerns about potential side effects. Nevertheless, she has remained in clinical and radiologic remission since discontinuing treatment in February 2025. Discussion This case highlights the diagnostic complexity of sarcoidosis, particularly in elderly patients with atypical abdominal involvement. Our patient was initially diagnosed with peripheral T-cell lymphoma (PTCL-NOS) at another institution based on imaging findings of generalized lymphadenopathy and ascites, along with lymph node and liver biopsies interpreted as suspicious for lymphoma. She was started on corticosteroids in anticipation of chemotherapy, highlighting how easily sarcoidosis can be mistaken for a malignant process, especially when granulomatous inflammation is misinterpreted in the absence of definitive clonality or atypia. In contrast, histopathological assessment at our institution, including additional tissue sampling, revealed non-caseating granulomas without evidence of malignancy. Both the EBUS-TBNA of mediastinal lymph nodes and laparoscopic omental biopsy demonstrated poorly formed epithelioid granulomas with no atypical lymphoid populations or necrosis. These findings, along with positive hilar and mediastinal lymphadenopathy on imaging and exclusion of infectious causes such as tuberculosis, supported the diagnosis of sarcoidosis. Intra-abdominal sarcoidosis is rare, and peritoneal involvement is even less common, accounting for less than 1% of cases in large case series. When present, it often poses a significant diagnostic challenge, as it can closely mimic lymphoproliferative disorders, peritoneal carcinomatosis, or tuberculous peritonitis, potentially leading to misdiagnosis and inappropriate initiation of cytotoxic or antimicrobial therapies. 3 , 4 In our case, the absence of malignant cells on repeated biopsies prompted reconsideration of the initial diagnosis, ultimately preventing unnecessary chemotherapy and its associated risks. PET imaging performed after steroid therapy demonstrated near-complete resolution of metabolic activity in the lymph nodes and omental tissue, correlating with the patient’s clinical improvement. This response is consistent with previously reported cases demonstrating rapid resolution of sarcoidosis-related lesions following corticosteroid therapy. 3 , 5 Sarcoidosis should therefore be considered in the differential diagnosis of unexplained intra-abdominal lymphadenopathy and ascites, particularly when imaging findings raise suspicion for malignancy but histological evaluation does not support a neoplastic process. Tissue confirmation remains the gold standard, as imaging alone cannot reliably distinguish sarcoidosis from mimics such as lymphoma, tuberculosis, or peritoneal carcinomatosis. 6 If unrecognized or left untreated, peritoneal sarcoidosis may progress to form tumor-like masses or multiple peritoneal nodules. 7 Chronic inflammation and adhesions can result in intestinal obstruction and eventually involve other organs, leading to organ dysfunction. 8 In addition, untreated peritoneal sarcoidosis can cause chronic pain, recurrent ascites, abdominal distension, and persistent discomfort, all of which may significantly impair daily functioning and quality of life. 9 Moreover, clinicians should remain aware of the sarcoidosis-lymphoma syndrome, a well-described phenomenon wherein patients with chronic sarcoidosis have an elevated risk of developing lymphoma. This association underscores the importance of vigilant long-term follow-up, even after apparent clinical remission. 10 Conclusion This case demonstrates that intra-abdominal sarcoidosis can closely mimic lymphoma both clinically and radiologically. Careful reconsideration of discordant imaging and histopathology, through exclusion of infectious and malignant etiologies, and prompt initiation of corticosteroid therapy are essential to avoid unnecessary chemotherapy and ensure favorable outcomes. Long-term surveillance remains essential given the recognized association between sarcoidosis and lymphoma. Declarations Ethics approval and consent to participate Not applicable. Consent for publication Written informed consent was obtained from the patient for publication of this case report and any accompanying images. Availability of data and materials The datasets generated and/or analysed during the current study are available from the corresponding author on reasonable request. Competing interests The authors declare that they have no competing interests. Funding No funding was received for the preparation or publication of this manuscript. Authors' contributions Nusaiba Al Maqrashi : Performed the case write-up. Masoud Kashoub : Initiated the project, organized the report, drafted the introduction and discussion, gathered radiology images, and created the table. Fathiya Al-Rahbi : Provided the pathology report and relevant histopathological images. Hawra Al Lawati, Jamal Al Aghbari, Ibrahim Al Busaidi, Asma Al Balushi : Critically reviewed the manuscript and provided expert input. Saif Al Mubaihsi : Final proofreading and content validation. All authors read and approved the final manuscript. Acknowledgements We would like to thank the patient for granting permission to share his case for educational purposes. Learning points : Intraabdominal sarcoidosis can closely mimic malignancy, particularly lymphoma, underscoring the importance of histopathologic confirmation before initiating chemotherapy. The presence of non-caseating granulomas without atypia or clonality across multiple biopsy sites should raise suspicion for sarcoidosis, even in elderly patients. Comprehensive exclusion of infectious etiologies, including tuberculosis and fungal infections, is essential prior to establishing a diagnosis of sarcoidosis. A favorable clinical and radiologic response to corticosteroids supports the diagnosis but should follow, not replace, a tissue-based and multidisciplinary evaluation References Hunninghake GW, Costabel U, Ando M, et al. ATS/ERS/WASOG statement on sarcoidosis. Sarcoidosis Vasc Diffuse Lung Dis. 1999;16(2):149–73. Sève P, Pacheco Y, Durupt F, et al. Sarcoidosis: A clinical overview from symptoms to diagnosis. Cells. 2021;10(4):766. 10.3390/cells10040766 . Lee SW, Lee MH, Lee JE, et al. Peritoneal sarcoidosis: A case report. Med (Baltim). 2019;98(24):e16001. 10.1097/MD.0000000000016001 . Papowitz AJ, Li JK. Abdominal sarcoidosis with ascites. Chest. 1971;59(6):692–4. 10.1378/chest.59.6.692 . Baughman RP, Lower EE, du Bois RM, Sarcoidosis. Lancet. 2003;361(9363):1111–8. 10.1016/S0140-6736(03)12888-7 . Michael H, Ho S, Pollack B, et al. Diagnosis of intra-abdominal and mediastinal sarcoidosis with EUS-guided FNA. Gastrointest Endosc. 2008;67(1):28–34. 10.1016/j.gie.2007.07.049 . Uthman IW, Bizri AR, Shabb NS, Khury MY, Khalifeh MJ. Peritoneal sarcoidosis: case report and review of the literature. InSeminars in arthritis and rheumatism 1999 Apr 1 (Vol. 28, No. 5, pp. 351–4). WB Saunders. Bellobono M, Cinalli M. Peritoneal sarcoidosis mimicking peritoneal carcinomatosis. Volume 8. ANNALI ITALIANI DI CHIRURGIA; 2019. Klingler F, Ashmawy H, Häberle L, Esposito I, Schimmöller L, Knoefel WT, Krieg A. Treatment pathways and prognosis in advanced sarcoma with peritoneal sarcomatosis. Cancers. 2023;15(4):1340. Fiorot CP, Rodrigues RS, Marchiori E. Sarcoidosis-lymphoma syndrome: A diagnostic dilemma. J Bras Pneumol. 2024;50(3):e20240105. 10.36416/1806-3756/e20240105 . Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 29 Jan, 2026 Reviews received at journal 20 Jan, 2026 Reviews received at journal 10 Jan, 2026 Reviewers agreed at journal 03 Jan, 2026 Reviewers agreed at journal 15 Dec, 2025 Reviewers agreed at journal 15 Dec, 2025 Reviewers agreed at journal 01 Dec, 2025 Reviewers invited by journal 20 Nov, 2025 Editor invited by journal 07 Nov, 2025 Editor assigned by journal 18 Sep, 2025 Submission checks completed at journal 18 Sep, 2025 First submitted to journal 18 Sep, 2025 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-7618197","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Case Report","associatedPublications":[],"authors":[{"id":548161086,"identity":"df81c47e-59e7-45e8-82d3-35701294c43b","order_by":0,"name":"Nusaiba Al Maqrashi","email":"","orcid":"","institution":"Oman Medical Speciality Board","correspondingAuthor":false,"prefix":"","firstName":"Nusaiba","middleName":"Al","lastName":"Maqrashi","suffix":""},{"id":548161087,"identity":"07e33966-6a79-4c4a-8f55-1d33c3c61040","order_by":1,"name":"Masoud 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with SUV max of \u003cstrong\u003e7.3\u003c/strong\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e(B)\u003c/strong\u003e Axial CT image from November \u0026nbsp;2023 \u0026nbsp;demonstrates reaccumulated ascites and hepatomegaly.\u003cstrong\u003e (C1)\u003c/strong\u003e Fused PET/CT image (May 2024) following therapeutic paracentesis shows metabolically active mediastinal lymph nodes with no residual ascites.\u003cbr\u003e\n \u003cstrong\u003e(C2)\u003c/strong\u003e MIP image from the same time point confirms stable disease activity without new FDG-avid lesions.\u003cbr\u003e\n \u003cstrong\u003e(D1)\u003c/strong\u003e Fused PET/CT image (June 2025) after systemic steroid therapy shows interval reduction in FDG uptake (SUV reduced from \u003cstrong\u003e4.0 to 2.3\u003c/strong\u003e) in previously noted lymphadenopathy.\u003cbr\u003e\n \u003cstrong\u003e(D2)\u003c/strong\u003e MIP image confirms complete metabolic response with no new or residual FDG-avid disease.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7618197/v1/1751be56042a355b5e57b34e.png"},{"id":97114421,"identity":"c3f37075-699f-4f43-846d-0c12e2d0a497","added_by":"auto","created_at":"2025-12-01 06:58:29","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":625291,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003ea.\u003c/strong\u003e\u003c/em\u003e\u003cem\u003e The omental biopsy specimen showed\u003c/em\u003e\u003cem\u003e\u003cstrong\u003e \u003c/strong\u003e\u003c/em\u003e\u003cem\u003ea nodule of poorly formed, non-caseating granuloma\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e(\u003c/em\u003e\u003cem\u003e\u003cstrong\u003ehematoxylin-eosin stain, H\u0026amp;Ex100).\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eFigure 2b\u003c/strong\u003e\u003c/em\u003e\u003cem\u003e. The granuloma showed central aggregates of epithelioid histiocytes, surrounded by a rim of lymphocytes \u003c/em\u003e\u003cem\u003e\u003cstrong\u003e(hematoxylin-eosin stain, H\u0026amp;Ex400).\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7618197/v1/108f0561f539f54d859a7bed.png"},{"id":97145366,"identity":"2f7d8547-1e1f-438e-8358-0c058ba3ee98","added_by":"auto","created_at":"2025-12-01 10:13:47","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2061053,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7618197/v1/ec2182b8-5eb7-408b-899e-91739b37dc40.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Sarcoidosis with Intraabdominal Involvement Mimicking Lymphoma: A Diagnostic Pitfall","fulltext":[{"header":"Introduction","content":"\u003cp\u003eSarcoidosis is a systemic inflammatory disease characterized by the formation of non-caseating granulomas in multiple organs, most commonly the lungs and thoracic lymph nodes.\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e While pulmonary involvement is the hallmark feature, sarcoidosis can manifest with a wide spectrum of extrapulmonary presentations that often pose diagnostic challenges. The incidence of sarcoidosis varies geographically, with higher prevalence observed among African Americans and Scandinavian population, and most patients present between 25 and 50 years of age.\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e However, sarcoidosis in elderly patients is less common and may present atypically, sometimes mimicking malignancy or other systemic diseases.\u003c/p\u003e\u003cp\u003eAbdominal sarcoidosis, including peritoneal involvement, is uncommon and may present with nonspecific findings such as ascites or intra-abdominal lymphadenopathy, which can easily be mistaken for other conditions such as metastatic cancer and lymphoproliferative disease.\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e In such scenarios, histopathological confirmation is essential for accurate diagnosis, as radiologic findings alone are often insufficient to distinguish it from malignancy or infectious etiologies such as tuberculosis. Here, we present a case of an elderly woman whose clinical presentation initially suggested malignancy. However, further evaluation at our center, including comprehensive tissue analysis, revealed an alternative etiology. The patient's clinical course and subsequent response to treatment emphasize the critical importance of re-evaluating cases with atypical clinical presentations and maintaining a broad differential diagnosis when initial findings are incongruent.\u003c/p\u003e"},{"header":"Case Presentation","content":"\u003cp\u003eWe present the case of a 61-year-old woman who was first seen at our institution in November 2023 in the hematology/lymphoma clinic for further evaluation of a presumptive diagnosis of peripheral T-cell lymphoma (PTCL-NOS). She had a 1-year history of vague epigastric pain, reduced appetite, and intermittent abdominal distension, along with intermittent low-grade fever, occasional nonproductive cough, and significant back pain. Six months prior, she had developed progressive abdominal swelling and was found to have moderate-to-large ascites and generalized lymphadenopathy.\u003c/p\u003e\u003cp\u003eA Positron Emission Tomography (PET) scan performed abroad in October 2023 showed a heterogeneous nodular lesion with mild Fluorodeoxyglucose (FDG) uptake in the pancreatic body, along with extensive lymphadenopathy involving periportal, portocaval, celiac, paraaortic, mesenteric, and mediastinal lymph nodes [images not shown]. Mediastinal, liver, and peripancreatic lymph node biopsies performed abroad had reportedly shown findings suspicious for PTCL-NOS, with a Ki-67 index of 10\u0026ndash;15% and pending CD30 immunostaining. She was empirically started on corticosteroids\u0026mdash;completed only a few days of therapy\u0026mdash;before being evaluated at our center, in preparation for chemotherapy.\u003c/p\u003e\u003cp\u003eHowever, at our center, the biopsy slides were reviewed by pathologists and found to be inconsistent with lymphoma. A repeat PET/CT scan in November 2023 demonstrated FDG-avid lymphadenopathy involving both the mediastinum and abdomen, with a subcarinal lymph node showing a maximum standardized uptake value (SUV max) of 7.3 (Fig.\u0026nbsp;1A1\u0026ndash;A2). Concurrent Computed Tomography (CT) imaging also revealed reaccumulation of ascitic fluid and hepatomegaly (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB). Given the discrepancy between imaging findings and histopathological results inconsistent with lymphoma, a comprehensive re-evaluation was undertaken.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAscitic fluid analysis, done several times and repeatedly revealed an exudative profile with Serum-Ascites Albumin Gradient(SAAG)\u0026thinsp;\u0026lt;\u0026thinsp;11 g/L, with a fluid albumin of 34 g/L, normal LDH, and lymphocytic predominance. Flow cytometry demonstrated mature T-cell predominance with an increased CD4:CD8 ratio and partial CD7 loss, but no evidence of clonal T-, B-, or Natural Killer (NK)-cell populations. An extensive infectious-disease evaluation\u0026mdash;including analyses of ascitic fluid and lymph-node tissue with acid-fast bacilli (AFB) staining, \u003cem\u003eMycobacterium tuberculosis\u003c/em\u003e GeneXpert testing and cultures, fungal cultures, and Q-fever serologies\u0026mdash;was negative or non-contributory. Serum Angiotensin-Converting Enzyme (ACE) level was 44 U/L, which was within the normal laboratory reference range (12\u0026ndash;68 U/L).\u003c/p\u003e\u003cp\u003eIn December 2023, she underwent endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) of mediastinal lymph nodes, which revealed epithelioid non-caseating granulomas. No malignant cells were seen, and AFB stain, Gene Xpert, and TB cultures were all negative [Not shown].\u003c/p\u003e\u003cp\u003eA laparoscopic omental biopsy performed in April 2024 demonstrated fibroadipose tissue containing scattered nodules of poorly formed, non-caseating granulomas composed of epithelioid histiocytes surrounded by a thin rim of lymphocytes (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e2\u003c/span\u003ea\u0026ndash;b). No atypia or malignant features were observed. Special stains including Periodic Acid\u0026ndash;Schiff (PAS), Grocott's Methenamine Silver (GMS), and Ziehl-Neelsen (ZN) were negative for microorganisms (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e2\u003c/span\u003ea\u0026ndash;b).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eA summary of all diagnostic investigations, key differential diagnoses, and the rationale for exclusion is presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Following multidisciplinary discussion and reasonable exclusion of infectious etiologies, she was started on oral prednisolone 20 mg once daily. After six weeks of therapy, her abdominal distension resolved and her overall well-being improved, with no further need for paracentesis.A follow-up PET/CT scan in May 2024 demonstrated stable mediastinal lymph nodes with no new FDG-avid lesions (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, C1\u0026ndash;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e2\u003c/span\u003e) and absence of ascites.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eSummary of Diagnostic Work-up and Differential Diagnosis\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCategory / Test\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFindings\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eDifferential Diagnoses Considered\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eReason Ruled Out\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eImaging\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePET/CT: FDG-avid mediastinal \u0026amp; abdominal lymphadenopathy; ascites; mild pancreatic FDG uptake\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eLymphoma, peritoneal carcinomatosis, tuberculosis\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eImaging alone non-specific; histology negative for malignancy or infection\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eAscitic Fluid Analysis\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eExudative; SAAG\u0026thinsp;\u0026lt;\u0026thinsp;11 g/L; albumin 34 g/L; normal LDH; lymphocyte-predominant\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eTB peritonitis, peritoneal carcinomatosis, lymphoma\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eCytology: no malignant cells; repeated cultures AFB/fungal negative\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eFlow Cytometry (Ascitic fluid)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMature T-cell predominance, \u0026uarr;CD4:CD8, partial CD7 loss; no clonal T-, B- or NK-cell populations\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePeripheral T-cell lymphoma\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNo clonal population or atypical lymphoid cells\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003ePathology \u0026ndash; Prior External LN/Liver Biopsies\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eInitially \u0026ldquo;suspicious for PTCL-NOS\u0026rdquo;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eLymphoma\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eReview at SQUH: no malignancy features, only granulomatous inflammation\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eEBUS-TBNA (Mediastinal lymph node)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eEpithelioid non-caseating granulomas; no malignant cells\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eLymphoma, TB, fungal infection\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eSpecial stains/cultures negative\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eOmental Biopsy\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePoorly formed non-caseating granulomas; PAS, GMS, Ziehl\u0026ndash;Neelsen stains negative\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eLymphoma, TB, fungal, IgG4-related disease\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNo atypia or microorganisms; histology classic for sarcoidosis\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eMicrobiologic Studies\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAFB stain, TB GeneXpert, TB cultures: negative; fungal cultures: negative; Q-fever serology: negative\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eTuberculosis, fungal peritonitis, Q-fever\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eAll negative\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eLaboratory\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eACE 44 U/L (normal); routine labs unremarkable\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u0026mdash;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eACE not elevated but normal ACE does not exclude sarcoidosis\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eClinical Course\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eExcellent response to corticosteroids; radiologic resolution\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eConfirms inflammatory granulomatous etiology\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMalignancy or infection unlikely with steroid-only resolution\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eTable 1\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;Comprehensive Diagnostic Work-up and Differential Diagnoses in a Patient with Intra-abdominal Sarcoidosis\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;Summary of all investigations performed, the key differential diagnoses considered (including lymphoma, tuberculosis, peritoneal carcinomatosis, fungal infections, IgG4-related disease, and Q-fever), and the rationale for exclusion of each condition, leading to the final diagnosis of systemic sarcoidosis with intra-abdominal involvement.\u003c/p\u003e\u003cp\u003eThe corticosteroid regimen was continued with gradual tapering over 6\u0026ndash;7 months. The patient remained clinically stable, and a repeat PET/CT scan in June 2025 demonstrated marked interval reduction in FDG uptake (SUV declined from 4.0 to 2.3) with no new sites of disease activity (Fig.\u0026nbsp;1D1\u0026ndash;D2), consistent with a complete metabolic response.\u003c/p\u003e\u003cp\u003eGiven the consistent histologic findings of non-caseating granulomas across multiple biopsy sites, the exclusion of malignant or infectious causes, and the excellent clinical and radiologic response to corticosteroids, a diagnosis of systemic sarcoidosis with intra-abdominal and mediastinal involvement was established. Although a longer course of corticosteroid therapy was recommended, the patient declined continuation because of concerns about potential side effects. Nevertheless, she has remained in clinical and radiologic remission since discontinuing treatment in February 2025.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis case highlights the diagnostic complexity of sarcoidosis, particularly in elderly patients with atypical abdominal involvement. Our patient was initially diagnosed with peripheral T-cell lymphoma (PTCL-NOS) at another institution based on imaging findings of generalized lymphadenopathy and ascites, along with lymph node and liver biopsies interpreted as suspicious for lymphoma. She was started on corticosteroids in anticipation of chemotherapy, highlighting how easily sarcoidosis can be mistaken for a malignant process, especially when granulomatous inflammation is misinterpreted in the absence of definitive clonality or atypia. In contrast, histopathological assessment at our institution, including additional tissue sampling, revealed non-caseating granulomas without evidence of malignancy. Both the EBUS-TBNA of mediastinal lymph nodes and laparoscopic omental biopsy demonstrated poorly formed epithelioid granulomas with no atypical lymphoid populations or necrosis. These findings, along with positive hilar and mediastinal lymphadenopathy on imaging and exclusion of infectious causes such as tuberculosis, supported the diagnosis of sarcoidosis.\u003c/p\u003e\u003cp\u003eIntra-abdominal sarcoidosis is rare, and peritoneal involvement is even less common, accounting for less than 1% of cases in large case series. When present, it often poses a significant diagnostic challenge, as it can closely mimic lymphoproliferative disorders, peritoneal carcinomatosis, or tuberculous peritonitis, potentially leading to misdiagnosis and inappropriate initiation of cytotoxic or antimicrobial therapies.\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e In our case, the absence of malignant cells on repeated biopsies prompted reconsideration of the initial diagnosis, ultimately preventing unnecessary chemotherapy and its associated risks. PET imaging performed after steroid therapy demonstrated near-complete resolution of metabolic activity in the lymph nodes and omental tissue, correlating with the patient\u0026rsquo;s clinical improvement. This response is consistent with previously reported cases demonstrating rapid resolution of sarcoidosis-related lesions following corticosteroid therapy.\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\u003cp\u003eSarcoidosis should therefore be considered in the differential diagnosis of unexplained intra-abdominal lymphadenopathy and ascites, particularly when imaging findings raise suspicion for malignancy but histological evaluation does not support a neoplastic process. Tissue confirmation remains the gold standard, as imaging alone cannot reliably distinguish sarcoidosis from mimics such as lymphoma, tuberculosis, or peritoneal carcinomatosis.\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e If unrecognized or left untreated, peritoneal sarcoidosis may progress to form tumor-like masses or multiple peritoneal nodules. \u003csup\u003e7\u003c/sup\u003e Chronic inflammation and adhesions can result in intestinal obstruction and eventually involve other organs, leading to organ dysfunction.\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e In addition, untreated peritoneal sarcoidosis can cause chronic pain, recurrent ascites, abdominal distension, and persistent discomfort, all of which may significantly impair daily functioning and quality of life.\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e Moreover, clinicians should remain aware of the sarcoidosis-lymphoma syndrome, a well-described phenomenon wherein patients with chronic sarcoidosis have an elevated risk of developing lymphoma. This association underscores the importance of vigilant long-term follow-up, even after apparent clinical remission.\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis case demonstrates that intra-abdominal sarcoidosis can closely mimic lymphoma both clinically and radiologically. Careful reconsideration of discordant imaging and histopathology, through exclusion of infectious and malignant etiologies, and prompt initiation of corticosteroid therapy are essential to avoid unnecessary chemotherapy and ensure favorable outcomes. Long-term surveillance remains essential given the recognized association between sarcoidosis and lymphoma.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eWritten informed consent\u003c/strong\u003e was obtained from the patient for publication of this case report and any accompanying images.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo funding was received for the preparation or publication of this manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cul type=\"disc\"\u003e\n \u003cli\u003e\u003cstrong\u003eNusaiba Al Maqrashi\u003c/strong\u003e: Performed the case write-up.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eMasoud Kashoub\u003c/strong\u003e: Initiated the project, organized the report, drafted the introduction and discussion, gathered radiology images, and created the table.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eFathiya Al-Rahbi\u003c/strong\u003e: Provided the pathology report and relevant histopathological images.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eHawra Al Lawati, Jamal Al Aghbari, Ibrahim Al Busaidi, Asma Al Balushi\u003c/strong\u003e: Critically reviewed the manuscript and provided expert input.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eSaif Al Mubaihsi\u003c/strong\u003e: Final proofreading and content validation.\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eAll authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe would like to thank the patient for granting permission to share his case for educational purposes.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLearning points :\u003c/strong\u003e\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003eIntraabdominal sarcoidosis can closely mimic malignancy, particularly lymphoma, underscoring the importance of histopathologic confirmation before initiating chemotherapy.\u003c/li\u003e\n \u003cli\u003eThe presence of non-caseating granulomas without atypia or clonality across multiple biopsy sites should raise suspicion for sarcoidosis, even in elderly patients.\u003c/li\u003e\n \u003cli\u003eComprehensive exclusion of infectious etiologies, including tuberculosis and fungal infections, is essential prior to establishing a diagnosis of sarcoidosis.\u003c/li\u003e\n \u003cli\u003eA favorable clinical and radiologic response to corticosteroids supports the diagnosis but should follow, not replace, a tissue-based and multidisciplinary evaluation\u003c/li\u003e\n\u003c/ul\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eHunninghake GW, Costabel U, Ando M, et al. ATS/ERS/WASOG statement on sarcoidosis. Sarcoidosis Vasc Diffuse Lung Dis. 1999;16(2):149\u0026ndash;73.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eS\u0026egrave;ve P, Pacheco Y, Durupt F, et al. Sarcoidosis: A clinical overview from symptoms to diagnosis. Cells. 2021;10(4):766. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.3390/cells10040766\u003c/span\u003e\u003cspan address=\"10.3390/cells10040766\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLee SW, Lee MH, Lee JE, et al. Peritoneal sarcoidosis: A case report. Med (Baltim). 2019;98(24):e16001. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1097/MD.0000000000016001\u003c/span\u003e\u003cspan address=\"10.1097/MD.0000000000016001\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePapowitz AJ, Li JK. Abdominal sarcoidosis with ascites. Chest. 1971;59(6):692\u0026ndash;4. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1378/chest.59.6.692\u003c/span\u003e\u003cspan address=\"10.1378/chest.59.6.692\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBaughman RP, Lower EE, du Bois RM, Sarcoidosis. Lancet. 2003;361(9363):1111\u0026ndash;8. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/S0140-6736(03)12888-7\u003c/span\u003e\u003cspan address=\"10.1016/S0140-6736(03)12888-7\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMichael H, Ho S, Pollack B, et al. Diagnosis of intra-abdominal and mediastinal sarcoidosis with EUS-guided FNA. Gastrointest Endosc. 2008;67(1):28\u0026ndash;34. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.gie.2007.07.049\u003c/span\u003e\u003cspan address=\"10.1016/j.gie.2007.07.049\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eUthman IW, Bizri AR, Shabb NS, Khury MY, Khalifeh MJ. Peritoneal sarcoidosis: case report and review of the literature. InSeminars in arthritis and rheumatism 1999 Apr 1 (Vol. 28, No. 5, pp. 351\u0026ndash;4). WB Saunders.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBellobono M, Cinalli M. Peritoneal sarcoidosis mimicking peritoneal carcinomatosis. Volume 8. ANNALI ITALIANI DI CHIRURGIA; 2019.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKlingler F, Ashmawy H, H\u0026auml;berle L, Esposito I, Schimm\u0026ouml;ller L, Knoefel WT, Krieg A. Treatment pathways and prognosis in advanced sarcoma with peritoneal sarcomatosis. Cancers. 2023;15(4):1340.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFiorot CP, Rodrigues RS, Marchiori E. Sarcoidosis-lymphoma syndrome: A diagnostic dilemma. J Bras Pneumol. 2024;50(3):e20240105. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.36416/1806-3756/e20240105\u003c/span\u003e\u003cspan address=\"10.36416/1806-3756/e20240105\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"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":"bmc-pulmonary-medicine","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pulm","sideBox":"Learn more about [BMC Pulmonary Medicine](http://bmcpulmmed.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/pulm/default.aspx","title":"BMC Pulmonary Medicine","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Lymphoma, Recurrent Ascites, Granuloma, Noncaseating, Sarcoidosis, Lymphadenopathy","lastPublishedDoi":"10.21203/rs.3.rs-7618197/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7618197/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cb\u003eBackground\u003c/b\u003e\u003c/p\u003e\u003cp\u003eSarcoidosis is a multisystem granulomatous disease with various manifestations. While pulmonary involvement is most common, intra-abdominal sarcoidosis is rare and often mimics malignancy, leading to misdiagnosis and delayed therapy.\u003c/p\u003e\u003cp\u003e\u003cb\u003eCase Presentation:\u003c/b\u003e\u003c/p\u003e\u003cp\u003eWe describe an elderly woman who was initially misdiagnosed with lymphoma at another center based on imaging demonstrating intra-abdominal lymphadenopathy and ascites and histopathological findings. She was started on corticosteroids in preparation for chemotherapy. Patient develooped recurrent ascites requring repeated paracentesis. However, reevaluation at our institution revealed non-caseating granulomas without malignant cells on omental biopsies. Additional investigations confirmed bilateral hilar and mediastinal lymphadenopathy, and comprehensive microbiological workup excluded infectious causes, including tuberculosis. Following a course of corticosteroid therapy, the patient experienced complete resolution of symptoms and near-complete radiologic improvement on follow-up PET imaging.\u003c/p\u003e\u003cp\u003e\u003cb\u003eConclusion\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThis case underscores the diagnostic challenges posed by sarcoidosis with atypical intra-abdominal involvement. Careful histological evaluation is critical to avoid misdiagnosis and inappropriate treatment. Familiarity with such uncommon clinical manifestations is critical for the accurate differentiation of sarcoidosis from other differential diagnosis, notably lymphoma, thereby ensuring timely initiation of effective therapy.\u003c/p\u003e","manuscriptTitle":"Sarcoidosis with Intraabdominal Involvement Mimicking Lymphoma: A Diagnostic Pitfall","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-01 06:58:24","doi":"10.21203/rs.3.rs-7618197/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-01-29T10:11:49+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-21T00:53:38+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-10T08:24:33+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"154865676892359920499007778722903794212","date":"2026-01-03T23:25:52+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"80389907527491505108618168316680373470","date":"2025-12-16T01:14:37+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"204143139604167615942879387002249367338","date":"2025-12-15T13:55:42+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"111491989435820653472458536146410638920","date":"2025-12-01T12:01:33+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-11-20T13:08:26+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-11-07T08:43:31+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-09-18T16:14:56+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-09-18T12:43:57+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Pulmonary Medicine","date":"2025-09-18T11:05:55+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-pulmonary-medicine","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pulm","sideBox":"Learn more about [BMC Pulmonary Medicine](http://bmcpulmmed.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/pulm/default.aspx","title":"BMC Pulmonary Medicine","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"bda2880d-3b00-4f2a-88ad-f98ba256787c","owner":[],"postedDate":"December 1st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-02-16T03:23:18+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-01 06:58:24","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7618197","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7618197","identity":"rs-7618197","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}