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

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.