A Rare Case of Ovarian Clear Cell Carcinoma Arising from an Endometriotic Cyst: A Case Report

Background: Endometriosis, characterized by ectopic endometrial tissue outside the uterus, commonly affects the ovaries and peritoneum. While generally benign, it has been linked to an increased risk of ovarian cancer, termed endometriosis-associated ovarian cancer (EAOC). Case Illustration: A 32-year-old woman experienced abdominal distension and a sense of fullness for one year. A gynecological examination revealed a right adnexal mass. Transvaginal ultrasound showed an enlarged uterus with adenomyosis features and a hyperhypoechoic, multilocular right adnexal mass (11.44 x 9.61 cm) with vascularization and septations. Transabdominal ultrasound indicated a complex ovarian cyst, bilateral mild hydronephrosis, and no metastases. Blood tests showed elevated CA-125 (318.60 U/mL), CA 19-9 (110.33 U/mL), and a high Risk of Malignancy Index (RMI: 955.80). Surgery included total abdominal hysterectomy, right salpingo-oophorectomy, omentectomy, and adhesiolysis. Pathological analysis confirmed endometriosis with atypical cells and clear cell carcinoma, classified as FIGO stage IIB. Post-surgery, the patient received six cycles of carboplatin and paclitaxel chemotherapy. Conclusion: EAOC is rare but highlights the elevated cancer risk in women with endometriosis, particularly for ovarian clear cell carcinoma. Early diagnosis and appropriate treatment are critical to reducing morbidity and mortality. Further research is needed to clarify the relationship between endometriosis and malignancy to improve preventive and therapeutic strategies.