Anal canal neoplasm Anal canal adenocarcinoma NCIT:C2852 UMLS:C1332259 Differentiating true anal canal adenocarcinoma from low rectal adenocarcinoma can be challenging. Most anal canal adenocarcinomas originate from anal glands, but cases developing in chronic tracts from fistula in ano are described. Multiple factors, including infection with HPV and HIV, history of receptive anal intercourse, smoking, and immunosuppression have been identified as risk factors. Clinical features include anal pain, induration of the anal canal, or abscess formation and a palpable lump. An adenoma carcinoma that originates in the anal canal. Adenocarcinoma of the large intestine