Anal duct carcinoma in a 70-year-old male with a history of prostate cancer

Anal duct (gland) carcinoma is a rare, under-recognized neoplasm of the anal canal. Histologically, it consists of haphazardly oriented neoplastic glands that proliferate beneath intact non-neoplastic squamous epithelium. Frequently, Pagetoid-like spread into the overlying squamous epithelium may be observed. Anal duct carcinoma is characteristically CK7+/CK20− by immunohistochemistry. We report a case of anal duct carcinoma diagnosed in a 70-year-old male with a history of treated prostate cancer. The epidemiology, clinical presentation, histologic features, differential diagnosis, treatment, and prognosis of anal duct carcinoma are discussed.