Concomitant abnormal accumulation of the p53 protein with either MDM2 overexpression or abnormal underexpression of p16 was significantly more frequent in tumoral tissue compared to normal tissue; p16-/p53+ immunostaining was detected in 20/50 (40%) tumors and in none of the normal tissues; whereas the opposite combination (p16+/p53-) was found in 11/50 (22%) tumors and 36/50 (72%) normal specimens, with a statistically significant difference between tumor and normal samples in these subgroups (P < 0.001). The gene discussed is CDKN2A; the disease is neoplasm.