PTEN and cancer: The depth of the invasion and the metastasis of the lymph nodes are very important prognostic features for the classification of melanoma; typically, this type of cancer is associated with a very heterogeneous tumour characterized by high mutational burden (e.g., BRAF, NRAS, PTEN, TP53, CDKN2A are the most frequently muted genes) and because of this, it is considered a particularly aggressive type of cancer [2].