Staging System Equivalents
The following excerpt is taken from Appendix B of
Colon & Rectal Cancer: A Comprehensive Guide for
Patients & Families by Lorraine Johnston, copyright 2000 by
O'Reilly & Associates, Inc. For book orders/information, call
(800) 998-9938. Permission is granted to print and distribute this
excerpt for noncommercial use as long as the above source is
included. The information in this article is meant to educate and
should not be used as an alternative for professional medical care.
Over time, various systems have been devised to describe the spread of colorectal cancer. The most recent staging system developed, the TNM system, is now the most commonly used in the US, as it is considered the most accurate and detailed.
Approximate TNM equivalents to older staging systems, the Dukes and Astler-Coller systems, are shown in the table below, although experts caution that the translation is not exact. A description of the terms used in the TNM system is included following the table.
In the TNM system, the terms and criteria for staging colon and rectal cancers are the same.
||Tis, N0, M0
||T1, N0, M0
T2, N0, M0
||A and B1
||T3, N0, M0
T4, N0, M0
||B2 and B3
||Any T, N1, M0
Any T, N2, M0
||C1 - C3
||Any T, Any N, M1
T: assessment of primary tumor
The following criteria are used by the National Cancer Institute to evaluate the extent of spread of the original tumor. At this point it might be useful to refer to the figure of a cross section of the colon. Going outward, the layers of the bowel are mucosa (comprised of epithelium, basement membrane, lamina propria, muscularis mucosae), submucosa, muscularis propria, subserosa. The serosa is an additional outer layer in areas of the peritoneal cavity where the bowel is freely moving:
- TX: The primary tumor cannot be evaluated.
- T0: The existence of a primary tumor cannot be ascertained.
- Tis: Carcinoma in situ (tumor in place): an intraepithelial tumor or an invasion of the lamina propria. Tis includes cancer cells entirely contained within the glandular basement membrane (intraepithelial) or lamina propria (intramucosal) with no breach through the muscularis mucosae into the submucosa.
- T1: The tumor invades the submucosa, the second layer of the large intestine.
- T2: The tumor invades the muscularis propria.
- T3: The tumor invades through the muscularis propria into the subserosa, or into nonperitonealized pericolic or perirectal tissues.
- T4: The tumor directly invades other organs or structures, and/or penetrates the visceral peritoneum. In T4, the term "direct invasion" includes invasion of other sections of colon or rectum by way of the serosa; for instance, invasion of the sigmoid colon by a carcinoma of the cecum.
N: assessment of regional lymph nodes
The following terms describe the criteria used to evaluate the degree to which lymph nodes have been invaded by cancerous cells:
- NX: Regional lymph nodes cannot be evaluated.
- N0: No invasion of regional lymph nodes (metastasis) is apparent.
- N1: Invasion of one to three regional lymph nodes has been found.
- N2: Invasion of four or more regional lymph nodes has been found.
M: assessment of distant metastasis
The following terms describe the criteria used to rank the spread of disease, if any, to distant organs:
- MX: Distant metastasis cannot be determined.
- M0: No distant metastasis is apparent.
- M1: Distant metastasis is apparent.
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