Ovarian clear cell carcinoma associated with endometriosis: a case report with immunohistochemical study.

Endometriosis is a frequent benign gynecological disease; nonetheless, it can demonstrate some aspects that resemble malignant disease. Malignant transformation of endometriosis occurs mainly in the ovary. A rare case of transition between typical endometriosis and clear cell carcinoma with immunohistochemical study is presented. The patient, a 30-year-old Caucasian woman (para 0), was diagnosed with endometriosis ten years before. Six months later she developed a left cystic ovarian tumor (58 cm3) that persisted after two ultrasounds in a four-month period. Tumor markers were normal (CA125, CA 15.3, CA 19.9, alpha-fetoprotein, carcinoembrionary antigen A1). There was no ascites. The left ovarian mass was removed by laparotomy and endometriosis in continuity with carcinoma positive for cytokeratin 7 and estrogen receptor was revealed. CD10 was positive in the stromal cells of the endometriosis. Clear cell carcinoma grade 3 was diagnosed. In conclusion, although a rare event, the association of typical endometriosis and clear cell carcinoma of the ovary should be kept in mind, mainly in patients with a persistent ovarian cyst.