Human Papillomavirus-Related Adenosquamous Carcinoma of the Anorectum With Pagetoid Spread

Adenosquamous carcinoma is an uncommon type of cancer that comprises malignant squamous and glandular components. We present a case of human papillomavirus (HPV)-positive adenosquamous carcinoma of the anorectum, which exhibited extensive pagetoid spread, in a 70-year-old woman. The tumor had spread from the lower rectum to the perianal skin and was removed through a combined endoscopic and transanal surgical procedure. Histological examination revealed three morphologically distinct components: adenocarcinoma in the lower rectum, squamous intraepithelial neoplasia with a minor invasive squamous cell carcinoma component in the anal canal, and pagetoid spread of adenocarcinoma extending to the perianal skin. HPV18 DNA and diffuse p16 expression were detected in all three components, suggesting the integration of HPV and a histogenetic relationship among these morphologically distinct components. This case indicates that HPV-associated adenosquamous carcinoma also occurs in the anal canal, similar to the uterine cervix, and may present as secondary Paget's disease.