Malignant melanoma arising in ovarian cystic teratoma

A 65-year-old Japanese woman with a primary malignant melanoma arising within a mature ovarian cystic teratoma is presented along with details of morphological examinations. The melanoma, found incidentally upon microscopic examination of the mature teratoma, consisted of cells showing radial and vertical growth and was surrounded by epithelium showing melanosis. This report describes the detailed morphological features of the malignant ovarian melanoma, which was of interest because of its small size and lack of peritoneal tumor cell dissemination.