Ovarian Clear Cell Carcinoma Detected During Long-Term Management of Endometriotic Cysts in Young Patients: Possible Heterogeneity of this Tumor

Ovarian endometriotic cysts have been identified as the possible origin of ovarian clear cell carcinoma (OCCC), so predicting or preventing future transformation is important. Early detection of clear cell carcinoma is important because it shows low sensitivity to chemotherapy and the prognosis is worse than for other histologic types. We recently treated 2 patients with OCCC. They were both young women with no family history of cancer who received long-term oral contraceptive therapy for endometriotic cysts, and the histologic diagnosis was typical clear cell carcinoma in both patients. However, in Case 1, the tumor was detected by periodic examination, tumor expression of WT1 was positive, and the stage was IA. On the other hand, Case 2 presented with fever of unknown origin, her tumor showed expression of p53, and the stage was IVB. Case 1 is alive with no evidence of disease at 38 months after surgery, while Case 2 died after 19 months despite intensive treatment. These contrasting cases suggest that we need to be aware of the risk of cancer in young women receiving long-term hormone therapy for endometriotic cysts and that OCCC may show greater heterogeneity than what has been reported previously.