Peritoneal melanosis associated with mucinous cystadenoma of the ovary and adenocarcinoma of the colon.

Peritoneal melanosis, a diffuse, black pigmentation of the peritoneum, is a very rare condition characterized by melanin pigment deposition in the peritoneum. In this paper, we describe a case of peritoneal melanosis associated with a mucinous cystadenoma on an ovary and adenocarcinoma in the colon of 68-year-old women. The patient was referred for an evaluation of lower abdominal pain and distension. Laboratory results showed anemia and elevated CA 125 levels. A pelvic computed tomographic scan revealed a huge multicystic mass on the right ovary and a well-enhancing intraluminal mass located at the rectosigmoid junction. During a surgical procedure, India-ink-colored (black) pigmentation was seen in the peritoneum, in the omentum, and on the surface of the ovary. Biopsies of the omentum and peritoneum showed pigment in the stroma and pigment-laden histiocytic aggregation. Pigment was also present in the wall of the mucinous cystadenoma of the ovary and colonic serosa. An ultrastructural study found melanosome in the cytoplasm of the histiocytes.