[Mitosis in early invasive malignant melanoma. How reliable is histogenetic classification at stage pT1?]

Since early February 2010 we have been implementing the latest version of the 2009 AJCC Melanoma Staging and Classification in our institution. Since, according to the guidelines for stage pT1 melanomas, the number of mitoses/mm(2) is of particular significance, we have been able to observe a notable shift from pT1a to pT1b. Highlighting the mitotic count as one of the key features of the diagnosis of malignant melanoma, we observed that the major part of stage-switched melanomas belonged to a minimally invasive subset of melanomas previously categorized as pT1a UICC (7(th) edition). A level of reasonable doubt remains regarding the distinct histogenetic classification of mitosis as early stage melanoma with regard to their epithelial or melanocytic origin.