CDK4 and cutaneous melanoma: Besides, the aberrations of CCND1 and CDK4/6 pathways have been documented to occur more frequently in acral melanoma than cutaneous melanoma, with the incidence being around 40% and 80%, respectively.38,39 The amplification rates of CDK4 and CCND1 are also frequently found in mucosal melanoma, with the incidence being 47.0% and 27.7%, respectively.40 Therefore, targeting the CDK4/6 pathway by specific inhibitor is hopeful to bring encouraging outcome for the treatment of acral melanoma and mucosal melanoma.