Ovarian Clear Cell Carcinoma: Report of Two Cases and Review of the Literature

Ovarian Clear Cell Carcinoma (OCCC) is an uncommon but clinically distinct subtype of epithelial ovarian cancer, characterized by unique molecular features, a strong association with endometriosis, an elevated risk of thromboembolic events, and relative resistance to platinum based chemotherapy. We describe two early stage OCCC cases with contrasting clinical contexts and management approaches. The first case involved a postmenopausal woman presenting with a very large cystic adnexal mass (21×20 cm) and completely normal serum tumor markers. She was ultimately diagnosed with FIGO stage IC1 disease following intraoperative cyst rupture caused by dense pelvic adhesions. Limited surgical staging was performed, and she subsequently received adjuvant platinum based chemotherapy. The second case involved a premenopausal woman with a history of endometriosis and an elevated ROMA index (CA 125 30 U/mL, HE4 70 pmol/L). She presented with a complex right adnexal mass and was diagnosed with FIGO stage IA OCCC, with endometriosis identified in the contralateral ovary. She underwent comprehensive surgical staging without adjuvant chemotherapy but later developed postoperative symptoms suggestive of pulmonary thromboembolism, for which she received one month of prophylactic apixaban. Both patients were enrolled in a standardized follow up protocol consisting of clinical examination and CA 125 assessment every three months, along with chest and abdominopelvic CT imaging every six months. These cases highlight several important clinical considerations: (1) normal serum tumor markers, including CA 125, do not exclude OCCC, even in the presence of very large adnexal masses; (2) the strong association between OCCC and endometriosis emphasizes the need for careful evaluation of complex adnexal lesions in women with endometriosis; (3) meticulous surgical staging including appropriate lymph node assessment and omental evaluation is essential for accurate FIGO classification and guiding adjuvant treatment decisions in early stage OCCC; and (4) the pronounced thromboembolic tendency of OCCC warrants heightened clinical vigilance and individualized thromboprophylaxis, even in patients with apparently limited stage disease.