21 | Melanoma in situ: long-term outcomes and follow-up strategies based on risk stratification

Beatrice De Checchi¹, Paolo del Fiore², Irene Russo², Chiara Trevisiol², Marco Domenico Mazza², Saveria Tropea², Francesco Russano², Mauro Alaibac³, Carlomaria Gianesini⁴, Giovanni Madeo⁴, Simone Mocellin^2|4 | ¹Department of Medicine, University of Padua, Padua; ²Soft-Tissue, Peritoneum and Melanoma Surgical Oncology Unit, Veneto Institute of Oncology IOV-IRCCS, Padua; ³Department of Dermatology, University of Padua; ⁴Department of Surgery, Oncology and Gastroenterology, University of Padua, Padua, Italy.

Background: In recent years, the rising incidence of melanoma in situ (MIS) has drawn increasing attention to treatment and follow-up strategies aimed at reducing the risk of recurrence and new primary melanomas. Interestingly, the increase in MIS diagnoses has not been paralleled by a rise in melanoma-specific mortality, suggesting potential overdiagnosis.

Methods: This study aimed to evaluate prognosis and recurrence rates in a cohort of MIS patients, comparing outcomes between excisional biopsy alone and excision followed by wider surgical margins. We also investigated clinico-pathological predictors of recurrence and the development of new primary melanomas, and proposed a risk-based model for personalized follow-up. We retrospectively reviewed data from 184 patients treated between 2019 and 2023 at Padova University Hospital and the Veneto Institute of Oncology. Collected variables included demographics, medical history, macroscopic and histopathological lesion characteristics, treatments, and follow-up outcomes. In the absence of disease-related recurrences or deaths, a composite risk variable (risk proxies) was constructed based on six risk indicators derived from literature evidence and their potential association with recurrence or second primary melanoma.

Results: Statistical analysis showed a significant association between age at diagnosis and high-risk classification, with patients >40 years more likely to be in the high-risk group. No significant differences were observed for sex, while lesion site and histotype showed trends toward significance. No local recurrences were observed in either group, and margin widening did not provide a statistically significant benefit in recurrence prevention.

Conclusions: Age at diagnosis is a key factor for MIS risk stratification and could guide a tailored follow-up strategy with closer surveillance for high-risk patients. Margin widening may not always be necessary, but prospective randomized studies are warranted to define standardized management.