Anal cancer. Microscopic condyloma and tissue demonstration of human papillomavirus capsid antigen and viral DNA.

Sixteen cases of squamous cell carcinoma of the anus, including 4 incidentally discovered in situ lesions, and 3 anal condylomas, were examined for the presence of human papillomavirus (HPV). All in situ tumors and 6 of the invasive tumors were associated with histologic changes typical of condyloma, despite the absence of clinical anogenital warts. Immunohistochemical studies for viral capsid antigen gave positive reactions in two anal warts and in the condylomatous area associated with one invasive tumor. In situ hybridization was accomplished using isotopic DNA probes for HPV 6/11, 16, 18, and 31. Human papillomavirus 6/11 was expressed in the corresponding capsid-positive regions in the two warts and the wart-associated invasive carcinoma. Both HPV 6/11 and HPV 16 were associated with one carcinoma in situ, and HPV 16 was also found within two invasive anal carcinomas, one of which was associated with an extensive vulvar cancer. While these observations do not resolve the "passenger" or direct oncogenic role for HPV in anal carcinoma, the circumstantial evidence is that the oncogenic influence is similar to that accepted for female genital tract cancer.