Abstract
Merkel cell carcinoma (MCC) is a relatively rare primary cutaneous neuroendocrine carcinoma with an incidence of approximately 3/1000000 per year, typically occurring in areas chronically exposed to sunlight (face, scalp, neck). The etiopathogenetic factors include mainly the action of Merkel polyomavirus (approximately 80% of all MCC), chronic ultraviolet exposure and a suppressed immune system.
Tumors associated with viral infection and those without are biologically distinct; tumors without proven virus have a significantly higher mutational load, including p53 and Rb mutations. From a therapeutic point of view, however, the distinction between the two subtypes of MCC is not yet crucial, as both have a similarly unfavorable prognosis and the same therapeutic management.
Histologically, MCC is a high-grade neuroendocrine carcinoma, in differential diagnosis it is necessary to distinguish, for example, small cell variant of melanoma, lymphohistiocytic neoplasms, Ewing's sarcoma and cutaneous metastases of neuroendocrine carcinomas of other primary origin. In case of diagnostic uncertainty, a second opinion at another pathology department can be used.