Epidemiology of Merkel cell carcinoma in Tuscany (Italy), 2006-2021.

Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer that still has a poor prognosis. MCC incidence has increased in recent years worldwide. The aim of our study was to perform an epidemiological retrospective study and to evaluate the impact of MCC clinical and pathological features on overall survival (OS) in a specific geographical area. We retrospectively collected 94 pathology reports from 2006 to 2021 that were present in the pathology archives of the University Hospital of Pisa and of the Hospital of Livorno. Laterality was different according to the site, and almost half of the lesions were T1 and nearly half of the patients had a clinical stage III. We reported a dramatic increase in MCC diagnoses in the last 5 years compared with the previous years, with a crude incidence rate of 1,15/100000 inhabitants, almost doubling the last reported data in Italy. Surgical margins status and ulceration were not related to OS. We have noticed some patients with a rapidly progressing disease and others showing a slow disease progression which should prompt the investigation of specific biomarkers or other features that could elucidate this striking difference in progression-free survival and could potentially identify different subtypes of MCC. Considering the generally low incidence of MCC worldwide, larger cohorts would be necessary to validate our data and to obtain a better prognostic stratification.