Clear cell borderline tumour of the ovary: a rare entity.

Borderline clear cell tumours of the ovary are exceedingly rare, with limited cases documented in literature. We present a case of a woman with primary infertility who presented with abnormal uterine bleeding and a history of bilateral endometriotic cysts. Abdominal examination revealed a mass of 17×12 cm. CT imaging showed a heterogeneous solid-cystic mass measuring 16.6×10.8 cm in the right adnexa with elevated cancer antigen 125 (CA-125) levels (761.9 IU/mL). Staging laparotomy was performed due to high suspicion of malignancy. Intraoperatively, a right ovarian mass of 18×14 cm size, with intact capsule, and a 3×3 cm left ovarian endometriotic cyst were found. Microscopically, the mass showed a multiloculated cyst wall lined by cuboidal epithelium, without significant nuclear atypia or stromal invasion, and was positive for Napsin A. The overall features were suggestive of clear cell borderline tumour. Postoperative CA-125 level was normalised and the patient was placed under regular follow-up.