Identifying high-risk features and improving follow-up strategies in thin melanoma: a retrospective cohort study

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BACKGROUND: Thin melanomas (TMs) are typically associated with favourable outcomes, but a subset of patients experience recurrence and worse survival. Prognostic factors for recurrence in TM remain inadequately characterized. OBJECTIVES: To identify clinical and histopathological factors associated with recurrence and explore implications for follow-up strategies in TM. METHODS: A retrospective cohort study included 308 patients with TM (Breslow thickness 0.1-1 mm) treated at two medical institutions between 1998 and 2017. Patients were stratified into groups with recurrence (n = 53) and no recurrence (n = 255). Clinical and histopathological variables were analysed, and survival outcomes were assessed. RESULTS: Recurrence (vs. no recurrence) was associated with nodular histology (13% vs. 3.1%, P = 0.02), presence of ulceration (17% vs. 2.7%, P < 0.001) and higher mitotic rate (mean 2.1 vs. 0.6 mitoses mm-2, P < 0.001). Ultrathin melanoma (Breslow ≤ 0.5 mm) was protective against recurrence (hazard ratio 0.08, P < 0.001). Recurrence (vs. no recurrence) reduced 10-year overall survival (62% vs. 95.7%, P < 0.001) and melanoma-specific survival (64% vs. 100%, P < 0.001). CONCLUSIONS: Prognostic factors such as ulceration, mitotic rate and histological subtype should guide individualized follow-up strategies. Ultrathin melanomas may require less intensive monitoring, while melanomas > 0.5 mm could benefit from extended follow-up beyond current guidelines. Tailoring surveillance based on recurrence risk could improve outcomes and quality of care for patients with TM.