Human papillomavirus-associated adenoma of the anorectum

Human papillomavirus (HPV) is the most common sexually transmitted disease in the United States. HPV-associated invasive anorectal adenocarcinoma has been previously described. In this study, we report the clinicopathological features of three HPV-associated anorectal adenomas.

A retrospective review of anorectal adenomas identified 46 in-house cases. Chromogenic in situ hybridization (CISH) for low- and high-risk HPV subtypes was performed, and high-risk HPV was detected in one (2.1%) case. Additionally, two consultation cases of HPV-positive anorectal adenomas were included, yielding a total of three cases (two females and one male, ages 58-63). All three tumours were located in the surgical anal canal and exhibited similar histologic features, characterized by a predominantly villous or villoglandular architecture with slit-like serrations. The tumour cells exhibited eosinophilic to mucinous cytoplasm with apical mucin cups. The nuclei were crowded and oval- to cigar-shaped. The chromatin was mostly smooth and delicate without prominent nucleoli. Additional immunohistochemistry performed on these HPV-positive adenomas revealed diffuse positivity for p16, CK7 and MUC5AC, with variable CDX2 expression.

HPV-associated anorectal adenomas are a distinct and rare entity. To the best of our knowledge, this is the first clinicopathological report of well-documented high-risk-HPV-associated anorectal adenomas. Increased awareness of this entity among pathologists will enable larger scale studies to further understand the pathogenesis of HPV-associated anorectal adenocarcinoma.