Melanosis Peritonei Associated With Adenocarcinoma of the Sigmoid Colon.

Melanosis peritonei is an unusual and uncommon condition characterized by pigment deposition in the peritoneum. It is usually associated with other conditions. During a right inguinal hernia open repair for an 86-year-old gentleman, widespread black spots were observed on the hernial sac. After appropriate histopathological and immunohistochemical studies, the diagnosis of melanosis peritonei was established. The past medical history of the patient included an endoscopic excision of a sigmoid polyp which was found to be an adenocarcinoma with <1mm clearance margin on histopathology. Being recognized as an extremely rare condition, melanosis peritonei should be differentiated from other conditions including metastatic melanoma.