Algorithmic approach to initial treatment for localized tumors of the anus, based on tumor location and histology

* Determination of the anatomic site of origin of carcinomas that overlap the anorectal junction can be problematic. For staging purposes, such tumors are classified as rectal cancers if their epicenter is located more than 2 cm proximal to the dentate line or proximal to the anorectal ring on digital examination, and as anal canal cancers if their epicenter is 2 cm or less from the dentate line. The majority of rectal squamous cell cancers represent anal squamous cell cancers that have extended into the distal rectum.
¶ Tumors that arise within the skin at or distal to the squamous mucocutaneous junction that can be seen in their entirety with gentle traction placed on the buttocks and are within 5 cm of the anus are classified as perianal skin cancers.
Δ Local excision may be an option for carefully selected patients with very favorable, superficially invasive tumors that are completely excised and have ≤3 mm of basement membrane invasion and a maximal horizontal spread of ≤7 mm. For the extremely aged population with T1N0 tumors or those with significant comorbidities, elimination of mitomycin and administration of fluorouracil alone during radiation therapy could be considered.