Malignant tumors of the anal canal: a comprehensive review

The proximity of the anal mucosa to the anal sphincters, the extensive blood supply and lymphatic drainage in this area, are important oncologic considerations. Lymphatic spread of anal canal lesions occurs in three different directions, superiorly to the mesorectal and superior hemorrhoidal nodes, laterally to the internal iliac nodes, and inferiorly to the inguinal and external iliac nodes. However, if obstruction exist, lymph can drain to the superior rectal nodes, or along the inferior rectal lymphatics to the ischioanal fossa.