CDKN2A and carcinoma: Thus, p16 may occur in the cytoplasm of carcinoma cells (colorectal, head and neck squamous cell, melanoma, astrocytomas; Straume et al., 2000; Zhao et al., 2003, 2012; Arifin et al., 2006), perhaps to inhibit nuclear function (Nilsson and Landberg, 2006).