CDKN2A and skin basal cell carcinoma: Most SCC in situ showed diffuse p16INK4a expression beginning in the parabasal cell layer, but no p16INK4a expression in the basal cell layer (Figure 3); 36.7% (11 out of 30) of the invasive SCC, 30.2% (16 out of 53) of the BCC, and 6.7% (1 out of 15) KA showed a diffuse p16INK4a expression pattern (Table 2; Figure 3).