Peritoneal melanosis associated with metastatic melanoma previously treated with targeted and immune checkpoint inhibitor therapy

Peritoneal melanosis associated with serous carcinoma of the ovary: A case report and literature review

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.

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Melanosis peritonei is an exceptionally benign condition of uncertain origin.

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Melanosis peritonei usually affects women between the ages of 18 and 28 years old.

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Melanosis peritonei is mostly associated with other disorders such as desmoid ovarian cyst, enteric duplication cyst, gastric triplication, and ovarian cystadenomas.

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The main differential diagnosis of melanosis peritonei is metastatic melanoma.

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.