Recurrence of a mature cystic teratoma: masquerading as a malignant neoplasm

We report a case of a mature cystic teratoma (MCT) of the ovary in a 44-year-old woman, characterized by both solid and cystic components derived from all three germ layers: ectoderm, endoderm, and mesoderm. This patient presented with non-specific abdominal discomfort and abdominal bloating for a couple of years. A pelvic ultrasound scan (USS) showed a large complex ovarian tumour with a CA 125 level of 74U/ml.
Due to the high calculated Risk of Malignancy Index (RMI), a diagnostic dilemma arose. Consequently, a total abdominal hysterectomy, salpingooophorectomy, and partial omentectomy were performed, given the suspicion of a malignant ovarian tumour. Macroscopically left ovary was enlarged with a nodular cystic mass. The cut surface showed a multilocular cyst filled with mucoid fluid. Some loculi contained hair and sebaceous material. Microscopically the solid areas of the cyst wall were largely composed of thyroid tissue (10%), the rest of the cyst wall contained mature skin adnexal structures including hair, salivary glands, adipose tissue, bone, lymphoid tissue and smooth muscle.