[Merkel cell carcinoma: a highly aggressive tumor with possible viral etiology]

Merkel cell carcinoma (MCC) or neuroendocrine carcinoma of the skin, is a rare and highly aggressive tumor which typically develops in chronically sun-damaged skin in aged or immunosuppressed patients. The clinical course is characterized by early local recurrence and lymphatic metastases. The current discussion on the etiology of MCC is dominated by the recently discovered Merkel cell polyoma virus (MCPyV). Apparently, MCPyV infection takes place early in life and the virus can also be found in healthy tissue. Possibly, a mutation of the viral genome is responsible for the development of the tumor. The 5 year survival rate of patients with primary MCC is only 30-40% after surgical therapy alone but can increase to about 75% after additional adjuvant radiotherapy. In cases with lymphatic or distant metastases various chemotherapy protocols in addition to operative and radiation therapy analogous to those for small cell lung cancer therapy have been found to be effective. Nevertheless, very high recurrence rates are typical in patients with distant metastases. Thus, MCC is regarded as chemosensitive but not chemocurable.Patients with MCC should be treated with an aggressive but individually adapted concept. The consequent integration of radiotherapy into the therapeutic approach can improve the prognosis.