Colon Cancer Staging 

Updated: Jan 09, 2018
  • Author: Lewis J Rose, MD; Chief Editor: N Joseph Espat, MD, MS, FACS  more...
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TNM Classification for Colon Cancer

The American Joint Committee on Cancer (AJCC) tumor/node/metastasis (TNM) classification and staging system for colon cancer are provided below. [1, 2]

See Benign or Malignant: Can You Identify These Colonic Lesions?, a Critical Images slideshow, to help identify the features of benign lesions as well as those with malignant potential.

Table 1. TNM Classification for Colon Cancer (Open Table in a new window)

Primary tumor (T)
TX Primary tumor cannot be assessed
T0 No evidence of primary tumor
Tis Carcinoma in situ: intraepithelial or or intramucosal carcinoma (involvement of lamina propria with no extension through the muscularis mucosa)
T1 Tumor invades submucosa (through the muscularis mucosa but not into the muscularis propria)
T2 Tumor invades muscularis propria
T3 Tumor invades through the muscularis propria into the pericolorectal tissues
T4 Tumor invades the visceral peritoneum or invades or adheres to adjacent organ or structure
T4a Tumor invades through the visceral peritoneum (including gross perforation of the bowel through tumor and continuous invasion of tumor through areas of inflammation to the surface of the visceral peritoneum)
T4b Tumor directly invades or is adherent to other organs or structures
Regional lymph nodes (N)
NX Regional lymph nodes cannot be assessed
N0 No regional lymph node metastasis
N1 Metastasis in 1-3 regional lymph nodes (tumor in lymph nodes measuring ≥0.2 mm) or any number of tumor deposits are present and all identifiable nodes are negative
N1a Metastasis in 1 regional lymph node
N1b Metastasis in 2-3 regional lymph nodes
N1c Tumor deposit(s) in the subserosa, mesentery, or nonperitonealized, pericolic, or perirectal/mesorectal tissues without regional nodal metastasis
N2 Metastasis in 4 or more lymph nodes
N2a Metastasis in 4-6 regional lymph nodes
N2b Metastasis in 7 or more regional lymph nodes
Distant metastasis (M)
M0 No distant metastasis by imaging or other studies, no evidence of tumor in distant sites or organs. (This category is not assigned by pathologists.)
M1 Metastasis to one or more distant sites or organs or peritoneal metastasis
M1a Metastasis confined to 1 organ or site (eg, liver, lung, ovary, nonregional node) without peritoneal metastasis
M1b Metastasis to two or more sites or organs without peritoneal metastasis
M1c Metastasis to the peritoneal surface alone or with other site or organ metastases

Table 2. Anatomic stage/prognostic groups (Open Table in a new window)

Stage T N M Dukes MAC
0 Tis N0 M0 -- --
I T1 N0 M0 A A
  T2 N0 M0 A B1
IIA T3 N0 M0 B B2
IIB T4a N0 M0 B B2
IIC T4b N0 M0 B B3
IIIA T1-T2 N1/N1c M0 C C1
  T1 N2a M0 C C1
IIIB T3-T4a N1/N1c M0 C C2
  T2-T3 N2a M0 C C1/C2
  T1-T2 N2b M0 C C1
IIIC T4a N2a M0 C C2
  T3-T4a N2b M0 C C2
  T4b N1-N2 M0 C C3
IVA Any T Any N M1a -- --
IVB



IVC



Any T



Any T



Any N



Any T



M1b



M1c



-- --

Staging information

Compared with the 7th edition of the AJCC staging manual, features of revised staging in the 8th edition give more importance to the poor prognostic features of depth of invasion in spite of fewer positive nodes.

  • T4 is divided between penetration to surface of visceral peritoneum and direct gross adherence to adjacent structures
  • T1-2N2 is downstaged from stage IIIC to IIIA or IIIB, depending on the number of nodes involved
  • Shift T4bN1 from IIIB to IIIC
  • Subdivide T4/N1/N2
  • Resolution of staging for issue of mesenteric deposits where nodal tissue is not identified
  • Revised substaging of stage II based on depth of invasion, with addition of stage IIC
  • Revised substaging of stage III based on node number (N1a—1 node; N1b—2-3 nodes; N2a—4-6 nodes; N2b—7 or more nodes)
  • Division of metastases to 1 or more sites in recognition of possibility of cure with aggressive treatment of single site of metastatic disease
  • Stage M1c has been introduced to represent the poor prognosis of peritoneal carcinomatosis.
  • Nodal micrometastases (tumor clusters ≥0.2 mm in diameter) are now scored as positive due to results of meta-analysis demonstrating poor prognosis in these patients. [3]
  • Other tumor deposits in peritoneum, subserosa, and mesentery are given equal weight as nodal metastases.

The following factors are important in determining treatment decisions but are not yet incorporated into the formal staging criteria:

  • A preoperative serum carcinoembryonic antigen(CEA) levels
  • Tumor regression score reflective of pathologic response to preoperative chemotherapy, chemoradiotherapy, radiotherapy, or chemobiologic therapy as well as status of circumferential margin for rectal cancer.
  • Lymphovascular and perineural invasion
  • Microsatellite instability (MSI), which represents deficiency of mismatch repair enzymes and is both a progostic factor and predictive of lack of response to fluoropyrimidine therapy in the adjuvant setting.
  • Mutation status of KRAS, NRAS, and BRAF, because mutations in those genes are associated with lack of response to agents targeting epidermal growth factor receptors.