Importance of Genetic Studies in Patients with Multiple Merkel Cell Carcinomas

Kamiyama et al. (1) recently reported a case of a 79-year-old woman with a history of a Merkel cell carcinoma (MCC) on her right cheek who underwent wide excision followed by adjuvant chemoradiation, and remained disease-free for 10 years, before presenting with a MCC on the left cheek. The tumour type was confirmed via histology and immunostaining, and both tumours were positive for Merkel cell polyomavirus (MCPyV) DNA by real-time polymerase chain reaction (RT-PCR) as well as immunostaining for the MCPyV large T antigen. The authors state that the two MCCs represent distinct primary tumours, and that their report is the first case of two primary MCCs of the skin with documented MCPyV infection. They reject the possibility that the second tumour could be a metastasis, based on the facts that: (