Consider the unexpected! An overlooked, elusive, rare but dramatic diagnosis: anorectal melanoma

TL;DR

Anorectal melanoma is a rare and aggressive cancer often misdiagnosed as benign, leading to poor outcomes despite early detection efforts.

Contribution

A multicenter retrospective study analyzing 21 cases of anorectal melanoma to highlight diagnostic challenges and outcomes.

Findings

Only 24% of patients had anorectal melanoma suspected at first presentation.

Median survival was 11 months for those with suspected AM and 24 months for incidentally diagnosed cases.

Most patients underwent wide local excision, with high postoperative recurrence rates.

Abstract

Background: Anorectal melanoma (AM) is a rare and aggressive malignancy, often misdiagnosed due to its clinical resemblance to benign anorectal conditions. Early diagnosis remains challenging, with a poor prognosis and high rates of metastasis at presentation. Methods: We conducted a retrospective multicenter study of 21 patients diagnosed with AM between 2013 and 2023 across four high-volume Italian surgical centers. Patients were stratified into two groups based on whether AM was suspected at initial evaluation (Group A) or incidentally diagnosed after surgery for presumed benign disease (Group B). Clinical, diagnostic, treatment, and outcome data were analyzed. Results: Only 24% of patients had AM suspected at first presentation. These patients were younger (median age 49 vs. 70 years) and had larger, more readily identifiable tumors. However, nodal and distant metastases were equally frequent in both groups (lymph node metastases: 52.4%; distant metastases: 19%). Most patients underwent wide local excision (71.4%), while only one required abdominoperineal resection. Postoperative recurrence occurred in 47.6% of cases. Median survival was 11 months in Group A and 24 months in Group B. In 90.5% of cases, previous specialist consultations had failed to achieve timely diagnosis, highlighting missed diagnostic opportunities. Conclusions: AM is frequently overlooked due to its rarity and non-specific presentation. Earlier recognition alone may not improve outcomes, but systematic histopathological assessment, targeted biopsy, and multidisciplinary management remain essential. Conservative surgery with early use of systemic therapy should be prioritized when feasible.

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