Ovarian Clear Cell Carcinoma: Report of Two Cases and Review of the Literature
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This report describes two early-stage ovarian clear cell carcinoma cases, highlighting the strong association with endometriosis, the limitations of serum tumor markers, and the risk of thromboembolic events.
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This case report describes two patients with ovarian clear cell carcinoma, highlighting the disease's distinct clinical features including resistance to platinum chemotherapy and a strong association with endometriosis. The first case involved a postmenopausal woman with normal tumor markers who experienced intraoperative cyst rupture due to dense adhesions, while the second was a premenopausal woman with known endometriosis who developed pulmonary thromboembolism despite early-stage disease. The authors emphasize that normal serum markers do not rule out this cancer type, meticulous surgical staging is critical for accurate classification, and heightened vigilance for thromboembolic events is required. This paper is centrally about endometriosis — specifically noting it as a significant risk factor and clinical context for the development of ovarian clear cell carcinoma in one of the reported cases.
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Abstract
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.
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Abstract
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.
Highlights
- OCCC may present with large ovarian masses despite normal tumor markers.
- Endometriosis is an important clinical context for ovarian clear cell carcinoma.
- Complete surgical staging is critical for accurate staging and treatment decisions.
- Dense adhesions and cyst rupture can complicate surgery and upstage early OCCC.
- OCCC warrants careful perioperative assessment of thromboembolic risk.
Keywords
Subjects
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- Receive Date 04 May 2026
- Revise Date 04 July 2026
- Accept Date 08 July 2026
- Publish Date 01 November 2026
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