RESUMO
Introduction: Melanosis peritonei is an exceptionally benign condition of uncertain origin marked by the deposition of dark pigments on the peritoneal cavity. It's usually associated with other abnormalities and must be differentiated from metastatic melanoma. Case presentation: We report this case of a 67-year-old female presented for abdominal distension for 16 months. Abdomino-pelvic CT scan showed a right pelvic ovarian mass locally developed with the presence of peritoneal ascites. We performed initially an exploratory laparotomy confirmed the radiological constatations with biopsies of the peritoneal carcinosis. Histologic analysis showed a poorly differentiated carcinomatous cell. The patient benefited from neoadjuvant chemotherapy then an abdomino-pelvic CT scan of control was performed showing the reduction in size of the ovarian mass and dispersion of the abdominal effusion. A second laparotomy was carried out and the exploration showed the appearance of dark nodules on the peritoneum. Hysterectomy associated with appendectomy and omentectomy with biopsy of the dark nodules was performed. Pathological study and immunohistochemical staining confirmed the diagnosis of benign peritoneal melanosis associated with serous carcinoma of the ovary. Discussion: Peritoneal melanosis is a rare condition with only 18 cases reported on the English literature. It is often associated with other conditions. The origin of this lesion still unclear although some hypotheses were reported. The main differential diagnosis is metastatic melanoma with very poor prognosis. Conclusion: benign peritoneal melanosis is a rare condition. Its management depends essentially on the associated disease.