Evidence of an epithelial origin of Merkel cell carcinoma

The current system of tumor classification relies largely on the recognition of a specific tumor cell morphology in conjunction with a unique immunophenotype 1 . Notably, molecular-genetic alterations occurring prior to or during tumor development contribute to the tumor cell development and its subsequent unique phenotype 2 . However, whether morphologic and genetic features always reflect the precise cell of origin remains controversial 2 , 3 , and for some tumor types, a precise identification of the cell of origin is not always available 4 . However, this remains a critically important challenge, as such findings have important implications for diagnosis, therapy and prevention 3 , 5 .