Unexpected Diagnosis of Struma Ovarii in a Patient with Bilateral Tubo-Ovarian Abscess: A Case Report

Unexpected Diagnosis of Struma Ovarii in a Patient with Bilateral Tubo-Ovarian Abscess: A Case Report | 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 Unexpected Diagnosis of Struma Ovarii in a Patient with Bilateral Tubo-Ovarian Abscess: A Case Report Sang Hoon Cheon, Jinhyuk Choi, Hyeong Sim Son, Won Moo Lee, Jeong Kyu Hoh, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7213112/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 30 Jan, 2026 Read the published version in BMC Women's Health → Version 1 posted 11 You are reading this latest preprint version Abstract Background Struma ovarii is a rare monodermal variant of ovarian teratoma that is predominantly composed of thyroid tissue. It accounts for a small fraction of ovarian tumors and is often diagnosed incidentally due to its typically asymptomatic nature or non-specific clinical presentation. Histologically, it resembles thyroid tissue and may present as a cystic or solid adnexal mass. We report an unexpected case in which a 48-year-old woman was clinically diagnosed with bilateral tubo-ovarian abscess based on imaging and intraoperative findings. However, postoperative histopathologic examination revealed struma ovarii in the right ovary. This case highlights the importance of considering uncommon pathological entities during evaluation of complex adnexal masses. Case Presentation A 48-year-old woman presented with acute lower abdominal pain. Imaging studies revealed bilateral adnexal cystic masses with features suggestive of tubo-ovarian abscess. Laparoscopic exploration identified dense adhesions and purulent material bilaterally, along with a distinct cystic lesion in the right ovary. Surgical intervention included right salpingo-oophorectomy and left salpingostomy. Histopathologic analysis confirmed struma ovarii in the right ovary and inflammatory changes consistent with abscess formation. The patient’s postoperative recovery was uneventful, and thyroid function remained within normal range. She continues to be disease-free during follow-up. Conclusions This case presents an uncommon diagnostic situation involving bilateral tubo-ovarian abscess with coexisting struma ovarii, in which the initial clinical impression was confined to tubo-ovarian abscess. The incidental identification of struma ovarii in the right ovary through postoperative histopathological evaluation highlights the relevance of comprehensive pathological assessment in patients with complex adnexal lesions. This observation suggests the benefit of maintaining a broad differential diagnosis and may offer additional context to gynecologic clinical decision-making. Struma ovarii mature cystic teratoma tubo-ovarian abscess laparoscopic surgery Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Background Struma ovarii is a rare ovarian neoplasm composed predominantly of ectopic thyroid tissue, accounting for approximately 0.3% of all ovarian tumors and 2.7% of ovarian teratomas[1,2]. Though typically benign, malignant transformation has been observed in 5–10% of cases[3,4,7]. Clinical presentations vary widely, often featuring nonspecific symptoms or remaining asymptomatic, which makes preoperative diagnosis particularly challenging[4]. Some patients may develop ascites, pleural effusion (pseudo-Meigs syndrome), or hyperthyroidism, although thyroid dysfunction is observed in only a minority[5,8]. Radiologic features frequently mimic other ovarian conditions, such as pelvic inflammatory disease, further complicating timely and accurate diagnosis[6]. The current case describes a 48-year-old female presenting with acute lower abdominal pain and radiologic signs consistent with bilateral tubo-ovarian abscess. Unexpectedly, histopathologic evaluation revealed struma ovarii in the right ovary with bilateral inflammatory changes[6]. This presentation emphasizes the importance of including rare ovarian tumors in the differential diagnosis of pelvic masses, particularly when clinical and imaging findings suggest acute inflammatory processes[6,8]. The case reinforces the need for heightened clinical awareness and thorough histological evaluation to avoid misdiagnosis and guide appropriate management. Case Report A 48-year-old woman presented to the gynecology outpatient clinic with acute lower abdominal pain. Transvaginal ultrasonography revealed a cystic mass measuring 8.0cm in the right adnexa and a 5.6cm cystic lesion in the left adnexa(Fig 1). Abdominopelvic computed tomography demonstrated septated cystic lesions measuring 8.5cm and 4.5cm in the right and left adnexa, respectively, accompanied by dilated tubular structures and fluid collection in the cul-de-sac, suggestive of bilateral tubo-ovarian abscess(Fig 2). Based on the clinical and radiologic findings, the patient underwent diagnostic laparoscopy under general anesthesia. Intraoperatively, both adnexa exhibited dense adhesions and inflammatory changes consistent with bilateral tubo-ovarian abscess. Abscess drainage was performed bilaterally. Additionally, a 4.5cm cystic mass was identified in the right ovary, distinct from the inflammatory lesions. Given the intraoperative findings, a right salpingo-oophorectomy and left salpingostomy were performed(Figs 3 and 4). Grossly, the cut surface of right ovarian mass showed multiloculated cystic lesion with gelatinous solid portion. On the microscopic examination, because this mass was composed predominantly of thyroid follicles without atypia, it was diagnosed as struma ovarii(Fig 5). The adnexal tissues showed diffuse acute suppurative and chronic inflammation, confirming the diagnosis of tubo-ovarian abscess. The patient recovered without complications and was discharged in stable condition following laparoscopic surgery. At the time of writing, thyroid function tests, including serum TSH, free T4, and total T3 levels, were performed to assess for potential functional activity of the ectopic thyroid tissue identified in the ovarian mass. All results were within normal limits, indicating no evidence of thyrotoxicosis or underlying thyroid dysfunction. The patient remained asymptomatic, with no residual abdominal pain, fever, or systemic complaints. She was scheduled for regular follow-up every six months, including clinical assessment and pelvic imaging. As of the latest follow-up, there was no evidence of disease recurrence or abnormal thyroid function. Discussion Struma ovarii is an uncommon ovarian tumor, typically presenting within a mature cystic teratoma[ 6 ]. Its diagnosis is often elusive due to nonspecific symptoms or incidental discovery[ 1 , 4 ]. Malignant transformation, while uncommon, has been reported in up to 30% of cases[ 3 , 7 ], with metastatic spread occasionally involving the peritoneum, omentum, or lungs[ 3 ]. In the present case, the concurrent presentation of bilateral tubo-ovarian abscess masked the underlying neoplasm and led to an initial misdiagnosis⁶. To our knowledge, such a co-presentation is exceedingly rare and not commonly reported in the literature[ 6 , 8 ]. This case emphasizes the diagnostic challenges posed by atypical adnexal masses that radiologically resemble inflammatory pathology[ 6 ]. The patient's age, bilateral involvement, and absence of thyroid dysfunction further underscore the unusual nature of this presentation[ 5 ]. Histopathological examination was instrumental in establishing the final diagnosis, reaffirming its critical role in evaluating adnexal masses with ambiguous clinical and imaging findings[ 2 ]. Our findings suggest that struma ovarii should remain a differential consideration, even in cases that clinically and radiographically suggest infectious or inflammatory disease[ 6 , 8 ]. Greater awareness of such atypical presentations may prevent diagnostic delays and ensure appropriate management[ 4 ]. Conclusions This case describes an uncommon clinical presentation of bilateral tubo-ovarian abscess with coexisting struma ovarii, diagnosed postoperatively through histological evaluation. The patient underwent successful surgical treatment and has shown no evidence of disease recurrence during follow-up. While struma ovarii is a rare entity, its incidental identification in a patient with complex adnexal pathology highlights the importance of maintaining a broad differential diagnosis in gynecologic practice. However, this report carries several limitations. First, the diagnosis of struma ovarii was made incidentally and retrospectively, without preoperative clinical suspicion, radiologic features, or utilization of thyroid-specific imaging modalities such as thyroid scintigraphy or serum thyrotropin levels. As a result, comprehensive endocrine workup, including thyroid function testing and autoantibody screening, was not performed. Second, the acute infectious presentation with prominent inflammatory features likely masked the underlying lesion, further complicating preoperative assessment. Third, as a single-case observation, the findings are inherently limited in generalizability and cannot establish causal relationships or management guidelines. Further case series and clinical studies are required to better elucidate the diagnostic characteristics and therapeutic considerations of struma ovarii, particularly when coexisting with pelvic infection. Declarations Acknowledgements : We would like to thank everyone who helped with this study. Author contributions : Sang Hoon Cheon: Visualization, Writing - original draft, Writing - review & editing. Jinhyuk Choi: Pathological examination and interpretation. Hyeong Sim Son: Provided institutional support throughout the research process. Won Moo Lee, Jung Kyu Ho, Jung Hye Hwang: Conceptual review and advisory support. Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. Conflicts of Interest The authors declare that they have no conflict of interest. Ethical Approval Ethical approval for this case report was waived by the Institutional Review Board of Hanyang University Hospital, as it involved a single anonymized patient. All procedures were conducted in accordance with the ethical standards of the Declaration of Helsinki. Consent to Participate and Publish Written informed consent for participation and publication was obtained from the patient included in this case report. Data Availability Statement The data used in this study are included in the article and its supplementary information files. References Devi P, Sriram K, Ramaswamy AS. Struma ovarii: a review of literature and a rare case report. J Clin Diagn Res . 2014;8(8):FD03–FD04. Young RH. New and unusual aspects of ovarian germ cell tumors. Am J Surg Pathol . 1993;17(12):1210–1224. Yassa L, Sadow PM, Marqusee E. Malignant struma ovarii: a series of 4 cases and a review of the literature. Endocr Pathol . 2008;19(2):103–110. Zhou J, Qu Y, Yang Q, Li L. Clinical and imaging features of struma ovarii: retrospective analysis of 15 cases. Radiol Med . 2021;126(2):233–240. Gustafson G, Roberts J, Kuller JA. Hyperthyroidism in pregnancy complicated by struma ovarii. Obstet Gynecol . 1991;77(3):512–515. Tang P, Yao J, Jiang M. Struma ovarii combined with pelvic inflammatory disease: a diagnostic challenge. Arch Gynecol Obstet . 2016;293(2):415–418. Makani S, Kim W, Gaba AR. Struma ovarii with a focus of papillary thyroid carcinoma: a case report and review of the literature. Gynecol Oncol . 2004;94(3):835–839. Roth LM, Talerman A. The enigma of struma ovarii. Pathology . 2007;39(1):139–146. Additional Declarations No competing interests reported. Supplementary Files Supplementarymaterial.docx SupplementarymaterialFig1.pdf SupplementarymaterialFig2.pdf SupplementarymaterialFig3.pdf SupplementarymaterialFig4.pdf SupplementarymaterialFig5.pdf Cite Share Download PDF Status: Published Journal Publication published 30 Jan, 2026 Read the published version in BMC Women's Health → Version 1 posted Editorial decision: Revision requested 26 Dec, 2025 Reviews received at journal 25 Dec, 2025 Reviewers agreed at journal 24 Dec, 2025 Reviewers agreed at journal 30 Aug, 2025 Reviews received at journal 18 Aug, 2025 Reviewers agreed at journal 08 Aug, 2025 Reviewers invited by journal 30 Jul, 2025 Editor assigned by journal 30 Jul, 2025 Editor invited by journal 29 Jul, 2025 Submission checks completed at journal 28 Jul, 2025 First submitted to journal 28 Jul, 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. 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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-7213112","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Case Report","associatedPublications":[],"authors":[{"id":493215447,"identity":"e730f795-b574-4950-9b81-430662da204e","order_by":0,"name":"Sang Hoon 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1","display":"","copyAsset":false,"role":"figure","size":275729,"visible":true,"origin":"","legend":"\u003cp\u003eTransvaginal sonographic image of bilateral adnexal masses\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7213112/v1/ce5d0782909eb5bdc95fd916.png"},{"id":88307410,"identity":"42d4c468-8aab-4cf4-9b3b-d592339a53ae","added_by":"auto","created_at":"2025-08-05 06:09:00","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":211617,"visible":true,"origin":"","legend":"\u003cp\u003eCoronal CT images showing bilateral adnexal masses\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7213112/v1/b25c2427f0c56dd6837fedcc.png"},{"id":88307408,"identity":"439f985a-6e70-4f2b-8819-41164a0827d8","added_by":"auto","created_at":"2025-08-05 06:09:00","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":380172,"visible":true,"origin":"","legend":"\u003cp\u003eThe right ovary cyst identified during laparoscopic surgery\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7213112/v1/d9fe3cd40a90eb1a864da717.png"},{"id":88307420,"identity":"c2d77ffc-1dff-4e44-8b61-332cee4fc595","added_by":"auto","created_at":"2025-08-05 06:09:01","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":382677,"visible":true,"origin":"","legend":"\u003cp\u003ePostoperative view following right salpingo-oophorectomy\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7213112/v1/2355e0b36dc5cf3bcf9c4b39.png"},{"id":88307415,"identity":"24d18575-0ea4-434b-8d07-874494dc5b50","added_by":"auto","created_at":"2025-08-05 06:09:01","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":542015,"visible":true,"origin":"","legend":"\u003cp\u003eThe microscopic findings of struma ovarii in the right ovary. A: The cystic lesion is composed of variable sized thyroid follicles with bland-cytologic features(H\u0026amp;E, x40). B: The thyroid follicles are lined by cuboidal cells without atypia, and occasionally filled with eosinophilic colloid(H\u0026amp;E, x100).\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7213112/v1/7ca477d8645557d1adc66210.png"},{"id":101690751,"identity":"12f2ccb6-21b9-44ca-b275-186fff4a721e","added_by":"auto","created_at":"2026-02-02 16:08:08","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2642272,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7213112/v1/4885ab2e-451b-45f9-853a-22d9f24ee4f4.pdf"},{"id":88307413,"identity":"80aedfaa-065e-4fb6-a778-297b89cbc53d","added_by":"auto","created_at":"2025-08-05 06:09:00","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":14396,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementarymaterial.docx","url":"https://assets-eu.researchsquare.com/files/rs-7213112/v1/834b96bf04322a5034933205.docx"},{"id":88307409,"identity":"dbc75cd5-9ab2-4d8e-9b9e-999254b5e9ed","added_by":"auto","created_at":"2025-08-05 06:09:00","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":149083,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementarymaterialFig1.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7213112/v1/1244174f0a424359f0a73cd5.pdf"},{"id":88307411,"identity":"9ff9aa95-a967-4f2e-b777-36d224c5165f","added_by":"auto","created_at":"2025-08-05 06:09:00","extension":"pdf","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":122729,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementarymaterialFig2.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7213112/v1/728a98b0a4a5e872b825f4cb.pdf"},{"id":88308632,"identity":"7b9b24d9-b528-4979-85eb-f6bb8449e037","added_by":"auto","created_at":"2025-08-05 06:25:01","extension":"pdf","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":126737,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementarymaterialFig3.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7213112/v1/979740c32cbf260c462fd456.pdf"},{"id":88307817,"identity":"491c6a31-0930-4eb4-aa9b-36119af6da26","added_by":"auto","created_at":"2025-08-05 06:17:01","extension":"pdf","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":126781,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementarymaterialFig4.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7213112/v1/4b119aa6bb6a89ad19e8f2e9.pdf"},{"id":88307406,"identity":"5dba2a2b-c000-4e4c-ace3-ee89fa46e498","added_by":"auto","created_at":"2025-08-05 06:09:00","extension":"pdf","order_by":5,"title":"","display":"","copyAsset":false,"role":"supplement","size":251212,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementarymaterialFig5.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7213112/v1/4475c65476a6445d9ba3e2c3.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Unexpected Diagnosis of Struma Ovarii in a Patient with Bilateral Tubo-Ovarian Abscess: A Case Report","fulltext":[{"header":"Background","content":"\u003cp\u003eStruma ovarii is a rare ovarian neoplasm composed predominantly of ectopic thyroid tissue, accounting for approximately 0.3% of all ovarian tumors and 2.7% of ovarian teratomas[1,2]. Though typically benign, malignant transformation has been observed in 5–10% of cases[3,4,7]. Clinical presentations vary widely, often featuring nonspecific symptoms or remaining asymptomatic, which makes preoperative diagnosis particularly challenging[4].\u003c/p\u003e\n\u003cp\u003eSome patients may develop ascites, pleural effusion (pseudo-Meigs syndrome), or hyperthyroidism, although thyroid dysfunction is observed in only a minority[5,8]. Radiologic features frequently mimic other ovarian conditions, such as pelvic inflammatory disease, further complicating timely and accurate diagnosis[6].\u003c/p\u003e\n\u003cp\u003eThe current case describes a 48-year-old female presenting with acute lower abdominal pain and radiologic signs consistent with bilateral tubo-ovarian abscess. Unexpectedly, histopathologic evaluation revealed struma ovarii in the right ovary with bilateral inflammatory changes[6]. This presentation emphasizes the importance of including rare ovarian tumors in the differential diagnosis of pelvic masses, particularly when clinical and imaging findings suggest acute inflammatory processes[6,8]. The case reinforces the need for heightened clinical awareness and thorough histological evaluation to avoid misdiagnosis and guide appropriate management.\u003c/p\u003e"},{"header":"Case Report","content":"\u003cp\u003eA 48-year-old woman presented to the gynecology outpatient clinic with acute lower abdominal pain. Transvaginal ultrasonography revealed a cystic mass measuring 8.0cm in the right adnexa and a 5.6cm cystic lesion in the left adnexa(Fig 1). Abdominopelvic computed tomography demonstrated septated cystic lesions measuring 8.5cm and 4.5cm in the right and left adnexa, respectively, accompanied by dilated tubular structures and fluid collection in the cul-de-sac, suggestive of bilateral tubo-ovarian abscess(Fig 2).\u003c/p\u003e\n\u003cp\u003eBased on the clinical and radiologic findings, the patient underwent diagnostic laparoscopy under general anesthesia. Intraoperatively, both adnexa exhibited dense adhesions and inflammatory changes consistent with bilateral tubo-ovarian abscess. Abscess drainage was performed bilaterally. Additionally, a 4.5cm cystic mass was identified in the right ovary, distinct from the inflammatory lesions. Given the intraoperative findings, a right salpingo-oophorectomy and left salpingostomy were performed(Figs 3 and 4).\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Grossly, the cut surface of right ovarian mass showed multiloculated cystic lesion with gelatinous solid portion. On the microscopic examination, because this mass was composed predominantly of thyroid follicles without atypia, it was diagnosed as struma ovarii(Fig 5). The adnexal tissues showed diffuse acute suppurative and chronic inflammation, confirming the diagnosis of tubo-ovarian abscess.\u003c/p\u003e\n\u003cp\u003eThe patient recovered without complications and was discharged in stable condition following laparoscopic surgery. At the time of writing, thyroid function tests, including serum TSH, free T4, and total T3 levels, were performed to assess for potential functional activity of the ectopic thyroid tissue identified in the ovarian mass. All results were within normal limits, indicating no evidence of thyrotoxicosis or underlying thyroid dysfunction. The patient remained asymptomatic, with no residual abdominal pain, fever, or systemic complaints. She was scheduled for regular follow-up every six months, including clinical assessment and pelvic imaging. As of the latest follow-up, there was no evidence of disease recurrence or abnormal thyroid function.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eStruma ovarii is an uncommon ovarian tumor, typically presenting within a mature cystic teratoma[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Its diagnosis is often elusive due to nonspecific symptoms or incidental discovery[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Malignant transformation, while uncommon, has been reported in up to 30% of cases[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], with metastatic spread occasionally involving the peritoneum, omentum, or lungs[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. In the present case, the concurrent presentation of bilateral tubo-ovarian abscess masked the underlying neoplasm and led to an initial misdiagnosis⁶. To our knowledge, such a co-presentation is exceedingly rare and not commonly reported in the literature[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThis case emphasizes the diagnostic challenges posed by atypical adnexal masses that radiologically resemble inflammatory pathology[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. The patient's age, bilateral involvement, and absence of thyroid dysfunction further underscore the unusual nature of this presentation[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Histopathological examination was instrumental in establishing the final diagnosis, reaffirming its critical role in evaluating adnexal masses with ambiguous clinical and imaging findings[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eOur findings suggest that struma ovarii should remain a differential consideration, even in cases that clinically and radiographically suggest infectious or inflammatory disease[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Greater awareness of such atypical presentations may prevent diagnostic delays and ensure appropriate management[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThis case describes an uncommon clinical presentation of bilateral tubo-ovarian abscess with coexisting struma ovarii, diagnosed postoperatively through histological evaluation. The patient underwent successful surgical treatment and has shown no evidence of disease recurrence during follow-up. While struma ovarii is a rare entity, its incidental identification in a patient with complex adnexal pathology highlights the importance of maintaining a broad differential diagnosis in gynecologic practice.\u003c/p\u003e\u003cp\u003eHowever, this report carries several limitations. First, the diagnosis of struma ovarii was made incidentally and retrospectively, without preoperative clinical suspicion, radiologic features, or utilization of thyroid-specific imaging modalities such as thyroid scintigraphy or serum thyrotropin levels. As a result, comprehensive endocrine workup, including thyroid function testing and autoantibody screening, was not performed. Second, the acute infectious presentation with prominent inflammatory features likely masked the underlying lesion, further complicating preoperative assessment. Third, as a single-case observation, the findings are inherently limited in generalizability and cannot establish causal relationships or management guidelines. Further case series and clinical studies are required to better elucidate the diagnostic characteristics and therapeutic considerations of struma ovarii, particularly when coexisting with pelvic infection.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e: We would like to thank everyone who helped with this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e:\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSang Hoon Cheon: Visualization, Writing - original draft, Writing - review \u0026amp; editing.\u003c/p\u003e\n\u003cp\u003eJinhyuk Choi: Pathological examination and interpretation.\u003c/p\u003e\n\u003cp\u003eHyeong Sim Son: Provided institutional support throughout the research process.\u003c/p\u003e\n\u003cp\u003eWon Moo Lee, Jung Kyu Ho, Jung Hye Hwang: Conceptual review and advisory support.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflicts of Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical Approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eEthical approval for this case report was waived by the Institutional Review Board of Hanyang University Hospital, as it involved a single anonymized patient. All procedures were conducted in accordance with the ethical standards of the Declaration of Helsinki.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Participate and Publish\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWritten informed consent for participation and publication was obtained from the patient included in this case report.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data used in this study are included in the article and its supplementary information files.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eDevi P, Sriram K, Ramaswamy AS. Struma ovarii: a review of literature and a rare case report. \u003cem\u003eJ Clin Diagn Res\u003c/em\u003e. 2014;8(8):FD03\u0026ndash;FD04.\u003c/li\u003e\n\u003cli\u003eYoung RH. New and unusual aspects of ovarian germ cell tumors. \u003cem\u003eAm J Surg Pathol\u003c/em\u003e. 1993;17(12):1210\u0026ndash;1224.\u003c/li\u003e\n\u003cli\u003eYassa L, Sadow PM, Marqusee E. Malignant struma ovarii: a series of 4 cases and a review of the literature. \u003cem\u003eEndocr Pathol\u003c/em\u003e. 2008;19(2):103\u0026ndash;110.\u003c/li\u003e\n\u003cli\u003eZhou J, Qu Y, Yang Q, Li L. Clinical and imaging features of struma ovarii: retrospective analysis of 15 cases. \u003cem\u003eRadiol Med\u003c/em\u003e. 2021;126(2):233\u0026ndash;240.\u003c/li\u003e\n\u003cli\u003eGustafson G, Roberts J, Kuller JA. Hyperthyroidism in pregnancy complicated by struma ovarii. \u003cem\u003eObstet Gynecol\u003c/em\u003e. 1991;77(3):512\u0026ndash;515.\u003c/li\u003e\n\u003cli\u003eTang P, Yao J, Jiang M. Struma ovarii combined with pelvic inflammatory disease: a diagnostic challenge. \u003cem\u003eArch Gynecol Obstet\u003c/em\u003e. 2016;293(2):415\u0026ndash;418.\u003c/li\u003e\n\u003cli\u003eMakani S, Kim W, Gaba AR. Struma ovarii with a focus of papillary thyroid carcinoma: a case report and review of the literature. \u003cem\u003eGynecol Oncol\u003c/em\u003e. 2004;94(3):835\u0026ndash;839.\u003c/li\u003e\n\u003cli\u003eRoth LM, Talerman A. The enigma of struma ovarii. \u003cem\u003ePathology\u003c/em\u003e. 2007;39(1):139\u0026ndash;146.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-womens-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmwh","sideBox":"Learn more about [BMC Women's Health](http://bmcwomenshealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bmwh/default.aspx","title":"BMC Women's Health","twitterHandle":"","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Struma ovarii, mature cystic teratoma, tubo-ovarian abscess, laparoscopic surgery","lastPublishedDoi":"10.21203/rs.3.rs-7213112/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7213112/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eStruma ovarii is a rare monodermal variant of ovarian teratoma that is predominantly composed of thyroid tissue. It accounts for a small fraction of ovarian tumors and is often diagnosed incidentally due to its typically asymptomatic nature or non-specific clinical presentation. Histologically, it resembles thyroid tissue and may present as a cystic or solid adnexal mass. We report an unexpected case in which a 48-year-old woman was clinically diagnosed with bilateral tubo-ovarian abscess based on imaging and intraoperative findings. However, postoperative histopathologic examination revealed struma ovarii in the right ovary. This case highlights the importance of considering uncommon pathological entities during evaluation of complex adnexal masses.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCase Presentation\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA 48-year-old woman presented with acute lower abdominal pain. Imaging studies revealed bilateral adnexal cystic masses with features suggestive of tubo-ovarian abscess. Laparoscopic exploration identified dense adhesions and purulent material bilaterally, along with a distinct cystic lesion in the right ovary. Surgical intervention included right salpingo-oophorectomy and left salpingostomy. Histopathologic analysis confirmed struma ovarii in the right ovary and inflammatory changes consistent with abscess formation. The patient’s postoperative recovery was uneventful, and thyroid function remained within normal range. She continues to be disease-free during follow-up.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis case presents an uncommon diagnostic situation involving bilateral tubo-ovarian abscess with coexisting struma ovarii, in which the initial clinical impression was confined to tubo-ovarian abscess. The incidental identification of struma ovarii in the right ovary through postoperative histopathological evaluation highlights the relevance of comprehensive pathological assessment in patients with complex adnexal lesions. This observation suggests the benefit of maintaining a broad differential diagnosis and may offer additional context to gynecologic clinical decision-making.\u003c/p\u003e","manuscriptTitle":"Unexpected Diagnosis of Struma Ovarii in a Patient with Bilateral Tubo-Ovarian Abscess: A Case Report","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-05 06:08:54","doi":"10.21203/rs.3.rs-7213112/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-12-26T08:46:07+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-25T18:37:07+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"45534283764101004455558693342167014868","date":"2025-12-24T08:14:45+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"250281338193329706871082023638921951842","date":"2025-08-30T12:55:53+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-18T17:41:52+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"264347683326593456222071919054233396981","date":"2025-08-08T14:16:40+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-30T09:21:54+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-07-30T09:13:08+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-07-29T08:26:40+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-07-28T15:10:38+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Women's Health","date":"2025-07-28T15:07:10+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-womens-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmwh","sideBox":"Learn more about [BMC Women's Health](http://bmcwomenshealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bmwh/default.aspx","title":"BMC Women's Health","twitterHandle":"","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"39bc13eb-878c-45ec-a074-adce50e64341","owner":[],"postedDate":"August 5th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-02-02T16:04:57+00:00","versionOfRecord":{"articleIdentity":"rs-7213112","link":"https://doi.org/10.1186/s12905-026-04302-8","journal":{"identity":"bmc-womens-health","isVorOnly":false,"title":"BMC Women's Health"},"publishedOn":"2026-01-30 15:58:28","publishedOnDateReadable":"January 30th, 2026"},"versionCreatedAt":"2025-08-05 06:08:54","video":"","vorDoi":"10.1186/s12905-026-04302-8","vorDoiUrl":"https://doi.org/10.1186/s12905-026-04302-8","workflowStages":[]},"version":"v1","identity":"rs-7213112","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7213112","identity":"rs-7213112","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}