Additionally, acral melanomas frequently harbor copy number gains in CCND1 and CDK4 and losses of CDKN2A, and a large preclinical study showed that palbociclib monotherapy was effective in treating acral melanoma patient derived xenograft tumors with various alterations to Cyclin–CDK circuitry [38]. Here, CDKN2A is linked to acral lentiginous melanoma.