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©2013 UpToDate ® Print Email TNM staging system for colorectal cancer, 6th edition Primary tumor (T)* Tis Carcinoma in situ; intraepithelial (within glandular basement membrane) or invasion of lamina propria (intramucosal) T1 Tumor invades submucosa T2 Tumor invades muscularis propria T3 Tumor invades through the muscularis propria into the subserosa, or into non-peritonealized pericolic or perirectal tissues T4 Tumor directly invades other organs or structures, and/or perforates visceral peritoneum• Regional lymph node (N)Δ NX Regional nodes cannot be assessed N0 No regional nodal metastases N1 Metastasis in 1 to 3 regional lymph nodes N2 Metastasis in 4 or more regional lymph nodes Distant metastasis (M) MX Distant metastasis cannot be assessed M0 No distant metastasis M1 Distant metastasis Stage groupings◊ Stage 0 Tis N0 M0 Stage I T1-2 N0 M0 Stage IIA T3 N0 M0 Stage IIB T4 N0 M0 Stage IIIA T1-2 N1 M0 Stage IIIB T3-4 N1 M0 Stage IIIC Any T N2 M0 Stage IV Any T Any N M1 * The completeness of resection of the primary tumor should be reflected by designation of the radial margin status (the surgically dissected surface adjacent to the deepest point of tumor invasion beyond the wall of the large bowel). R0: complete tumor resection, with all margins negative; R1: incomplete tumor resection with microscopic margin involvement; R2: incomplete tumor resection with gross residual tumor that was not resected. • Direct invasion in T4 includes invasion of other segments of the colorectum by way of the serosa. Tumor that is adherent to other organs or structures, macroscopically, is classified T4. However, if no tumor is present in the adhesion, the classification should be pT3. V and L substaging should used to denote the presence or absence of vascular or lymphatic invasion. Δ A tumor nodule in the pericolorectal adipose tissue of a primary carcinoma without histologic evidence of residual lymph node in the nodule is classified as a regional nodal metastasis if the nodule has the form and smooth contour of a lymph node. If it has an irregular contour, it should be classified in the T category, and also coded as V1 (microscopic venous invasion) or V2 (if it was grossly evident), because of the strong likelihood that it represents venous invasion. ◊ The y prefix is used for those cancers that are classified following treatment, whereas the r prefix is used for recurrent cancers.

* The completeness of resection of the primary tumor should be reflected by designation of the radial margin status (the surgically dissected surface adjacent to the deepest point of tumor invasion beyond the wall of the large bowel). R0: complete tumor resection, with all margins negative; R1: incomplete tumor resection with microscopic margin involvement; R2: incomplete tumor resection with gross residual tumor that was not resected. • Direct invasion in T4 includes invasion of other segments of the colorectum by way of the serosa. Tumor that is adherent to other organs or structures, macroscopically, is classified T4. However, if no tumor is present in the adhesion, the classification should be pT3. V and L substaging should used to denote the presence or absence of vascular or lymphatic invasion. Δ A tumor nodule in the pericolorectal adipose tissue of a primary carcinoma without histologic evidence of residual lymph node in the nodule is classified as a regional nodal metastasis if the nodule has the form and smooth contour of a lymph node. If it has an irregular contour, it should be classified in the T category, and also coded as V1 (microscopic venous invasion) or V2 (if it was grossly evident), because of the strong likelihood that it represents venous invasion. ◊ The y prefix is used for those cancers that are classified following treatment, whereas the r prefix is used for recurrent cancers. Used with the permission of the American Joint Committee on Cancer (AJCC), Chicago, Illinois. The original source for this material is the AJCC Cancer Staging Manual, Sixth Edition (2002) published by Springer-Verlag New York, Inc.