Anal Cancer
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Anatomy_of_the_anus_utd_jan_2007.jpg (32333 bytes) The anus consists of a mucosa-lined anal canal and an epidermis-lined anal margin. The proximal end of the anal canal begins anatomically at the junction of the puborectalis portion of the levator ani muscle and the external anal sphincter, and extends distally to the anal verge, a distance of approximately 4 cm. The anal canal is divided by the dentate line, which overlies the transition from glandular (columnar) to squamous mucosa that is often referred to as the transitional zone. The anal margin begins approximately at the anal verge, which corresponds to the introitus of the anal orifice. It represents the transition from the squamous mucosa to the epidermis-lined perianal skin, and extends to the perianal skin.

At initial presentation, most patients have a T1 or T2 lesion and fewer than 20 percent are node-positive. In a series of 270 patients with anal canal SCC, the distribution of stage at diagnosis was as follows

  • T1 — 9 percent
  • T2 — 51 percent
  • T3 — 30 percent
  • T4 — 10 percent
  • Node-positive — 13 percent

 In the above series of 270 patients, the five-year survival by stage was

  • T1 — 86 percent
  • T2 — 86 percent
  • T3 — 60 percent
  • T4 — 45 percent
  • N0 — 76 percent
  • Node-positive — 54 percent

 

 

patients with squamous cell carcinoma of the anal canal are generally treated with wide local excision for in-situ cases (if margins are negative) or with radiation. The more advanced cases get radiation usually combined with chemotherapy (see NCCN guidelines for anal canal). Patients with cancer of the anal margin may be treated with local surgery (see guidelines for anal margin). Following this, patients are checked every few months (without biopsy unless there is a suspicious area, see NCCN follow-up guidelines.) Go here for NCCN anal site