Human papillomavirus‐associated adenoma of the anorectum

Aims 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. Methods and results 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. Conclusions 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.