When a Dermoid Turns Deadly: A Rare Case of Adenocarcinoma Arising in a Mature Cystic Teratoma of the Ovary

Abstract

Introduction: Mature cystic teratoma is a common benign ovarian germ-cell tumour, whereas malignant transformation is rare and occurs predominantly in older women. Squamous cell carcinoma is the most frequent malignancy arising within these tumours, while adenocarcinoma is exceptionally uncommon and may mimic primary ovarian or metastatic gastrointestinal adenocarcinoma.

Aim & Objective: To describe the clinicopathological features of a rare case of adenocarcinoma arising within an ovarian mature cystic teratoma and to emphasize the importance of thorough histopathological evaluation and exclusion of an extraovarian primary.

Case Presentation: A 59-year-old woman presenting with a large abdominopelvic mass suspected to be ovarian in origin was evaluated. Ultrasonography, serum CA-125 assessment, surgical excision, and detailed histopathological examination were performed. The resected specimen was extensively sampled, particularly the solid and necrotic areas, to identify malignant transformation and correlate the findings with the mature teratomatous components.

Results: Ultrasonography revealed a 20.0 × 15.1 cm multiloculated hypoechoic abdominopelvic lesion with mild ascites. Serum CA-125 was approximately 180 U/mL. The patient underwent surgical excision of the ovarian mass with the uterus, cervix, and bilateral adnexa. Histopathological examination demonstrated mature tissues derived from all three germ layers along with malignant glandular proliferation, confirming adenocarcinoma arising within a mature cystic teratoma.

Conclusion: Adenocarcinoma arising within a mature cystic teratoma represents an exceptionally rare form of somatic malignant transformation. It should be considered particularly in postmenopausal women presenting with large ovarian masses. Thorough sampling and histopathological assessment are essential for diagnosis, while exclusion of an extraovarian primary adenocarcinoma is crucial. Complete excision, appropriate staging, and structured oncological follow-up are important for management and prognostic assessment.

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