ABSTRACT
Patterns of Tumor Spread Carcinoma of the anus is an indolent disease, which usually becomes locally extensive before distant metastases occur. Anatomical localization is important as it reflects the pattern of spread. According to the American Joint Committee on Cancer (AJCC), cancers are classified as anal tumors if their epicenter is less than or equal to 2 cm from the dentate line. They are rectal cancers if their epicenter is more than 2 cm proximal to the dentate line. Anal margin lesions are distal to the anal verge, where hair-bearing skin occurs. Anal canal cancers are of greater concern because they are more likely to invade the sphincters and spread deep into the pelvis via lymphatics and hemorrhoidal veins.
