Thin and in situ melanoma: an update for the dermatologist.

BACKGROUND: Thin melanoma (TM, ≤1.0 mm Breslow thickness) and Melanoma In Situ (MIS) constitute the majority of melanoma diagnoses worldwide and are responsible for melanoma-related deaths in these early-stage tumors. Despite their favorable prognosis, MIS and TM represent an opportunity for improving patient outcomes through early detection, accurate risk stratification, and long-term surveillance for metastasis and new skin neoplasms. OBJECTIVE: Provide an update of current evidence regarding epidemiology, risk factors, prognostic indicators, genetic background, and clinical management of MIS and TM. METHODS: A comprehensive review of the literature and international guidelines was conducted, integrating epidemiologic data, clinical prognostic parameters, and molecular insights relevant to MIS and TM. RESULTS: MIS and TM account for over 80% of all melanomas, with increasing incidence and relatively stable mortality rates. Prognosis is primarily determined by Breslow depth and ulceration, while factors such as mitotic rate, anatomic site, and age further refine risk assessment. Genetic alterations contribute to tumorigenesis but are not yet integrated into routine management. Long-term dermatological surveillance is needed, as new neoplasms, recurrence, and metastasis can develop during follow-up. CONCLUSIONS: MIS and TM are increasingly diagnosed, and dermatologists need to be a part of early detection, multidisciplinary management, and lifelong surveillance, which remain the cornerstone of reducing melanoma-related mortality. STUDY LIMITATIONS: The substantial heterogeneity among the included studies limits direct comparison and quantitative synthesis of the available data.