Anorectal melanoma: systematic review of the current literature of an aggressive type of melanoma

Anorectal melanoma (ARM) is a rare malignancy often associated with a poor prognosis due to its late diagnosis and aggressive biological behavior. This review aims to comprehensively investigate ARM's diagnosis, management, and treatment, emphasizing its clinical characteristics, laboratory findings, and implications for patient prognosis. A systematic literature search was conducted in PubMed, Embase, and Cochrane CENTRAL databases from inception to 1 July 2024. This review synthesizes existing literature to provide a comprehensive understanding of this rare primary malignancy. A total of 110 articles reporting on 166 patients were included. Gender data were available for 131 cases, comprising 67 females (51.1%) and 64 males (48.9%). The median age was 66 years. The overall median time to diagnosis was 4 months for anal melanoma, 3 months for rectal melanoma, and 4 months for anorectal junction melanoma. The clinical presentation was nodular in 98.2% of cases. Pre-diagnosis symptoms included bleeding in 84.9% of cases, mucous elimination (6%), pain (68.7%), tenesmus (16.9%), and changes in bowel movements (28.5%). Overall survival (OS) was reported in 82 cases, with a median OS of 11 months: 11 months for anal melanoma, 7 months for rectal melanoma, and 12 months for anorectal junction melanoma. ARM is a rare and aggressive melanoma subtype often diagnosed at an advanced stage, leading to a poor prognosis. A female predominance was observed, consistent with other mucosal melanomas. Anal melanoma exhibited better progression-free survival, and OS compared to rectal and anorectal junction melanoma.