Melanoma is among the most aggressive malignancies. Tumors with a thickness of 4 mm can produce metastases, and the mean survival of the patients is 9 months. The review presents modern classification of the melanoma types based on cytological and morphological indices (Clark model). Alterations of genes in melanomas are discussed in detail. These genes include tumor suppressors, proliferative response genes (oncogenes), and transcription factors. Alterations in the Wnt signaling, MAPK cascade, and Fas signaling pathways are considered. Changes in the mismatch repair (MMR) genes are also analyzed. From practical perspective, understanding the genetic alterations provides identification of potential targets for therapeutic exposure and enables prognosis of the tumor response to chemotherapy.