Further in support of a role for TRAF2 in skin tumorigenesis, mutations of the TRAF2-deubiquitinating enzyme CYLD are identified in patients with familial cylindromatosis, a condition that results in benign tumors of skin appendages, and CYLD−/− mice are highly susceptible to chemically induced skin tumors (122). Here, CYLD is linked to familial cylindromatosis.