CDKN2A and cervical cancer: In the two cervical cancer, three penile SCC and four penile LS cases where p16INK4A was strongly expressed and no HPV was detected, the levels of HPV may be too low for detection or HPV types may be present that are not amplified by the SPF10 system.18 In the absence of HPV infection p16INK4A expression is frequently inhibited by methylation or mutation in penile SCC21,32 and nonpenile cutaneous SCC.33 Inactivation of p16INK4A indirectly by HPV or by methylation and mutation therefore appears to be an important step in penile tumorigenesis.