After the accumulation of various mutations in the genes controlling cell cycle, such as cyclin-dependent kinase inhibitor 2A (CDKN2A), TP53, phosphatase and tensin homolog (PTEN) and genes encoding SWI/SWF chromatin remodeling complex subunits, particularly ARID1A and ARID2, primary melanoma enters the vertical growth phase and becomes malignant melanoma [28,29]. The gene discussed is PTEN; the disease is melanoma.