Early ovarian clear cell carcinoma. Clear cell carcinoma of the right ovary, most probably originating from endometriosis. The macroscopic picture in the very early stage may be difficult to distinguish from a benign endometrioma or another benign ovarian tumor. The preoperative assessment including transvaginal sonography and tumor marker CA-125 is important in the risk assessment (e.g. according to the IOTA criteria) and crucial for the correct surgical therapy of the patient. Arrows: various peritoneal endometriotic lesions and old blood deposits.