Warty carcinoma of the anus: a variant of squamous cell carcinoma associated with anal intraepithelial neoplasia and human papillomavirus infection

Abstract

Warty carcinoma (WC) is a rare variant of squamous cell carcinoma primarily described in the vulva in younger women and classically associated with human papillomavirus (HPV) infection. The gross findings are similar to those of verrucous carcinoma with large, exophytic tumors with a papillomatous surface. Microscopically, the tumor is papillated and contains fibrovascular cores covered by hyperkeratotic epithelium showing presence of koilocytes. We report a case of anal squamous cell carcinoma showing similar features, occurring in a young immunosuppressed male patient with a history of multifocal anal intraepithelial neoplasia (AIN). HPV-16 has been demonstrated both in the WC and in adjacent AIN, but the HPV status appears different in the two lesions: integrated in WC and episomal in AIN lesions. We also have demonstrated by immunohistochemistry that both WC and AIN are highly proliferative entities sharing the same MIB-1 pattern, and that WAF1/CIP1 protein expression is common in the two lesions irrespective of p53 protein expression.