ANATOMY
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ANATOMY
RULES FOR CLASSIFICATIONS DEFINITION OF TNM STAGE GROUPING HISTOPATHOLOGIC TYPE HISTOPATHOLOGIC GRADE (G) PROGNOSTIC FACTORS BIBLIOGRAPHY |
Manual for Staging of Cancer; Fifth Edition; Edited by Irvin D. Fleming, M.D., Jay S. Cooper, M.D., Donald Earl Henson, M.D., Robert V.P. Hutter, M.D., B.J. Kennedy, M.D., Gerald Murphy, M.D., D.S.c., Brian O'Sullivan, M.B., F.R.C.P.C., F.R.C.P.I., Leslie H. Sobin, M.D., John W. Yarbro, M.D., Ph.D.; Copyright 1997, the American Joint Committee on Cancer. Published by Lippincott-Raven Publishers. Chapter 13, pp. 91 - 96.
| C21.0 | Anus, NOS |
| C21.1 | Anal canal |
| C21.2 | Cloacogenic zone |
| C21.8 | Overlapping lesion of rectum, anus and anal canal |
Two different staging systems are needed for carcinomas that arise in the anal canal, one for carcinomas arising in the anal canal proper and the other for carcinomas arising at the anal margin. The two systems are needed because carcinomas that arise in these sites have different modes of spread and treatment options.
Carcinomas of the anal canal are staged clinically according to the size and extent of the primary tumor. Thus, patients with cancer of the canal can be classified at presentation by inspection of the lesion and palpation of adjacent structures, including the regional lymph nodes. Although additional information concerning depth of penetration is often provided by the pathologist after resection, in many cases, especially those initially treated with radiation and chemotherapy, the depth of invasion cannot always be assessed. Radiation and chemotherapy not only destroy tumor cells but also cause inflammatory changes and edema, which often makes it difficult for the pathologist to assess the extent of disease. The most important indicator of outcome is spread of tumor outside the pelvis. Lymph nodes should be specifically identified.
Cancers that arise at the anal margin, that is, the junction of the hair-bearing skin and the mucous membrane of the anal canal, or more distal, are staged according to the system used for cancers of the skin (see Chapters 23 and 24).
ANATOMY
Primary Site. The anal canal extends from the rectum to the perianal skin and is lined by a mucous membrane that covers the internal sphincter. The mucous membrane extends to the junction of the hair-bearing skin.
Regional Lymph Nodes. For pN, histologic examination of a regional perirectal-peripelvic lymphadenectomy specimen will ordinarily include 12 or more regional lymph nodes; or histologic examination of an inguinal lymphadenectomy specimen will ordinarily include 6 or more lymph nodes. The regional lymph nodes are as follows:
Perirectal:
Anorectal
Perirectal
Lateral sacral
Internal iliac (hypogastric)
Inguinal:
Superficial
Deep femoral
All other nodal groups represent sites of distant metastasis. The sites of regional node involvement are governed by the lymphatic drainage, above to the rectal ampulla and below to the perineum. Tumors that arise in the anal canal usually spread initially to the anorectal and perirectal nodes, and those that arise at the anal margin spread to the superficial inguinal nodes.
Metastatic Sites. Cancers of the anus can metastasize to most organs, especially to the liver and lungs. Involvement of the abdominal cavity is not unusual.
RULES FOR CLASSIFICATION
The staging system does not preclude the surgeon from recording the depth of penetration or extension of tumor based on information provided by the pathologist or radiologist. This information, however, is not included in the staging classification.
Metastasis to other nodal groups, such as the inferior mesenteric, can often be suspected by computed tomography (CT) or magnetic resonance imaging (MRI).
Clinical Staging. Anal cancers are staged primarily by inspection and palpation. Imaging may help to define the extent of tumor. In rare cases of rectal excision, tumors of the anal canal may be staged pathologically. Direct invasion of the rectal wall, perirectal skin, or subcutaneous tissue is not considered T4. The tumor is classified by size.
DEFINITION OF TNM
| TX | Primary tumor cannot be assessed |
| T0 | No evidence of primary tumor |
| Tis | Carcinoma in situ |
| T1 | Tumor 2 cm or less in greatest dimension |
| T2 | Tumor more than 2 cm but not more than 5 cm in greatest dimension |
| T3 | Tumor more than 5 cm in greatest dimension |
| T4 | Tumor of any size invades adjacent organ(s), e.g., vagina, urethra, bladder (involvement of the sphincter muscle[s] alone is not classified as T4) |
| NX | Regional lymph nodes cannot be assessed |
| N0 | No regional lymph node metastasis |
| N1 | Metastasis in perirectal lymph node(s) |
| N2 | Metastasis in unilateral internal iliac and/or inguinal lymph node(s) |
| N3 | Metastasis in perirectal and inguinal lymph nodes and/or bilateral internal iliac and/or inguinal lymph nodes |
STAGE GROUPING
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HISTOPATHOLOGIC TYPE
HISTOLOGIC GRADE (G)
PROGNOSTIC FACTORS
BIBLIOGRAPHY
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Flam MS, John M, Lovalvo LJ, et al: Definitive non-surgical therapy of epithelial malignancies of the anal canal. Cancer 51:1378-1387, 1983
Greenall MJ, Quan SHQ, Stearns MW, et al: Epidermoid cancer of the anal margin. Am J Surg 149:95-101, 1985
Longo WE, Vernava AM 3rd, Wade TP, et al: Recurrent squamous cell carcinoma of the anal canal: predictors of initial treatment failure and results of salvage therapy. Ann Surg 220:40-49, 1994
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Nigro ND: Treatment of squamous cell cancer of the anus. Cancer Treat Res 18:221-242, 1984
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Roseau G, Palazzo L, Colardelle P, et al: Endoscopic ultrasonography in the staging and follow-up of epidermoid carcinoma of the anal canal. Gastrointest Endosc 40:447-450, 1994
Salmon RJ, Fenton J, Asselain B, et al: Treatment of epidermoid anal canal cancer. Am J Surg 147:43-47, 1984
Salmon RJ, Zafrani B, Labib A, et al: Prognosis of cloacogenic and squamous cancers of the anal canal. Dis Colon Rectum 29:336-340, 1986
Schraut WH, Wang CH, Dawson PJ, et al: Depth of invasion, location, and size of cancer of the anus dictate operative treatment. Cancer 51:1291-1296, 1983
Scott NA, Beart RW Jr, Weiland LH, et al: Carcinoma of the anal canal and flow cytometric DNA analysis. Br J Cancer 60:56-58, 1989
Shank B: Treatment of anal canal carcinoma. Cancer 55(Suppl):2156-2162, 1985
Shepherd NA, Scholefield JH, Love SB, et al: Prognostic factors in anal squamous carcinoma: A multivariate analysis of clinical, pathological and flow cytometric parameters in 235 cases. Histopathology 16:545-555, 1990
Spratt JS (Ed.): Neoplasms of the colon, rectum, and anus. Philadelphia, WB Saunders, 1984
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