Histological predictors of the unfavorable outcome of anorectal melanoma

AIM: to find histological prognostic factors for survival in patients with anorectal melanoma.
PATIENTS AND METHODS: single center retrospective study of histological specimens of patients with anorectal melanoma (2005-2023). A revision of histological specimens was carried out, using the following criteria: multifocal growth, maximum tumor size, maximum thickness by Breslow, ulceration, perineural and lymphovascular invasion, as well as depth of invasion. Statistical processing was carried out using the Cox regression.
RESULTS: twenty-one patients were included in the study. In all patients, treatment started with surgery: 13 (61.9%) — abdominoperineal excision (APE); 8 (28.1%) — local excision). The sample contained patients with the following initial stages of the process: IB–IIB — 12 (57.1%); III — 9 (42.9%). Nine (42.9%) patients developed local recurrence, and 8 (38.1%) — distant metastases. On univariate analysis, DFS was significantly affected by ulceration RR 0.061 (CI 95.0%; 0.004–0.097, p = 0.048), there was a trend towards the role of neurotropism RR 3.654 (CI 95.0%; 0.934–14.297, p = 0.063) and pigmentation RR 2.485 (CI 95.0%; 0.832–7.424, p = 0.103). In multivariate analysis, none of the criteria had a significant effect on DFS. On OS in univariate analysis was a trend towards an effect of Breslow invasion depth of more than 2 cm HR 1.028 (CI 95.0%; 0.998–1.060, p = 0.070) and depth of tumor invasion HR 2.117 (CI 95.0%; 0.990–4.525, p = 0.053). In multivariate analysis, none of the criteria had a significant effect on OS.
CONCLUSION: evaluation of the effectiveness by histological features of skin melanoma showed the potential use of neurotropism, Breslow invasion of more than 2 cm and depth of tumor invasion as factors of unfavorable impact on DFS and OS in ARM. More trials are needed.

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