Characterization of different clinical presentations of Merkel cell carcinomas and their potential prognostic implications

Background Recent studies have analysed the impact of Merkel cell polyomavirus (MCPyV) on the clinical features and prognosis of patients with Merkel cell carcinoma (MCC). However, there are currently no available data on specific morphological clinical differences of MCC according to MCPyV-positive (MCPyV+) and -negative (MCPyV-) status and any possible prognostic implications of the different clinical presentations.Objectives To describe the clinicopathological characteristics of patients with MCC and the prevalence of MCPyV infection in an Italian cohort of patients and to define possible differences in clinicopathological and prognostic features among MCPyV+ and MCPyV- MCCs.Methods A retrospective, multicentre cohort study was conducted in two Italian tertiary referral centres. MCPyV presence was detected by immunohistochemistry and real-time polymerase chain reaction (RT-PCR) with two different primer sets, amplifying the viral protein (VP1) or large T antigen (LT) viral regions (VP1-PCR and LT-PCR, respectively). Clinicopathological features were compared between MCPyV+ and MCPyV- tumours and between red exophytic nodules and subcutaneous cyst-like MCCs.Results Of the 62 MCCs that were included, 43 (69%) presented as red exophytic nodules and 12 (19%) with a subcutaneous cyst-like appearance; MCPyV was detected in 25 cases (40%) by IHC, 35 (56%) by VP1-PCR and 49 (79%) by LT-PCR. No correlation was found between clinical morphology and viral status. Mortality rate was higher for MCPyV- cases (77%) than for MCPyV+ (23%) (P = 0.239) and higher for red nodules (70%) than for cyst-like lesions (59%) (P = 0.005). By multivariable analysis, age at diagnosis, Ki67 proliferation index and treatment with surgery/radiotherapy remained the only factors significantly affecting overall survival.Conclusions This study highlights the potential impact of clinical morphology of MCCs on prognosis. Subcutaneous cyst-like morphology may provide a survival benefit to the patients, regardless of MCPyV status.Recent studies have analysed the impact of Merkel cell polyomavirus (MCPyV) on the prognosis of patients with Merkel cell carcinoma (MCC); however, there are no available data on specific morphological clinical differences of MCC according to MCPyV positivity or negativity and any prognostic implications of different clinical presentations. Our retrospective observational study found two different clinical presentations of MCC: red exophytic nodules and subcutaneous cyst-like lesions. Our results suggest that a subcutaneous cyst-like morphology may provide a survival benefit to patients, regardless of MCPyV status.