Metachronous Merkel cell carcinoma on both cheeks.

Merkel cell carcinoma (MCC), an aggressive skin cancer with neuroendocrine features, has been found to be associated with a new type of human polyomavirus called Merkel cell polyomavirus (MCV). Patients diagnosed with MCC have a significantly increased risk of a second primary cancer. We report here the first case of two primary MCCs arising on the face at different times, associated with MCV infection. The tumour on the patient's right cheek was surgically removed, followed by chemoradiation. After a 10-year tumour-free period, a new tumour developed on the patient's left cheek. Histological and immunohistochemical findings were consistent with MCC. The tumours had high MCV copy numbers and expressed large T antigen, which may play a major role in MCV-mediated carcinogenesis. This case highlights the close links between MCC and MCV.