[Merkel cell carcinoma: diagnostic and treatment]

Merkel cell carcinoma (MCC) is an uncommon neuro-endocrine tumor of the sun-exposed skin predominantly observed in white patients in the sixth decade of the life. In electron microscopy MCC characteristically contains dense core secretory granules. This tumor expresses both epithelial (keratins of low molecular weight of the simple epithelial type, epithelial membrane antigen) and neuro-endocrine markers (neuron-specific enolase, chromogranin A). The analysis of available literature indicates that MCC has a propensity for involvement of regional lymphatics (12% of patients at the date of initial diagnosis and 50 to 66% afterwards) and for metastases to distant sites (20 to 52%). The prognosis of metastatic disease is poor. The overall survival from the diagnosis of metastases is 6 months. The optimal treatment of locoregional stages should include excision and post-operative radiation. The role of chemotherapy in this tumor is unclear but recent data suggest a high chemosensitivity.