Primary rectal melanoma in an African female: a case report

Primary malignant melanoma occurs frequently on the skin and is rare in people of African ancestry. The rectal region is an unusual site for non-cutaneous melanoma. We report a case of a 58-year- old African woman presenting to a Kenyan hospital with lower abdominal pain and per rectal bleeding for three months, who underwent a colonoscopy that showed a rectal polypoid mass at the anorectal region. Histology of the mass showed pigmented pleomorphic cells which had positive stains for melanoma markers. Staging workup performed, including magnetic resonance imaging (MRI) of the pelvis and positron emission tomography (PET) - computed tomography (CT), showed regional lymph node involvement but no evidence of distant metastases. Surgery was recommended to the patient but she died eight months after the diagnosis. The case illustrates that primary rectal melanoma, though rare in Africans, is an aggressive disease which can be easily misdiagnosed as hemorrhoids or rectal adenocarcinoma.