Because karyotype abnormalities have frequently been reported in melanocytic lesions and a high frequency of heterozygosity loss has been demonstrated in chromosome 9, it has been proposed that this chromosome contains one or more tumor suppressor genes that may also be involved in squamous cell and basal cell carcinomas.13-17 p16INK4a is a tumor suppressor protein encoded by the CDKN2A gene in the 9p21 region, a gene that can generate different transcripts. This evidence concerns the gene CDKN2A and basal cell carcinoma.