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Staging of colon and rectum cancer

The extension of the cancer (stage) is classified according to the TNM- (UICC/AJCC) system.

The cancer stage at the time of diagnosis

The size and depth penetration of the tumor is (T), regional lymph node metastases (N), and/or distant metastases (M). Based on TNM four stages are constructed. The TNM system is frequently revised: TNM 5.ed. 1997, TNM 6.ed. 2002, TNM 7. ed 2010. The number of the applied version should always be given as the criterias varies between the versions.

Tumor depth penetration (T)

  • Carcinoma in situ
    • High grade intraepithelial neoplasia, previously called high grade dysplasia.
    • Intramucosal neoplasia (infiltration onto, but not through the lamina propria and muscularis mucosa).
  • T1:  Infiltration of submucosa
    • Flat T1 tumors is sub classifies according to Kudo/Kikuchi in three groups.
      • sm1-3 according to the penetration depth into submucosa. This is of practical importance when a local excision is considered.
    • T1 in pedunculated polyps are classified according to Haggit. This is of practical importance for the evaluation of the radicality of a sling resection .
  • T2:  Infiltration of muscularis propria.
  • T3:  Infiltration through the intestinal wall into subserosa /pericolic (rectal).
  • T4a: Infiltration into and through the visceral peritoneum (TNM 7.ed 2010).
  • T4b: Infiltration into surounding organs (TNM 7.ed 2010). T4a/b was the other way around in previous version.

T1

T2-3

T4

Lymph node status (N)

  • N0: No presence of metastatic lymph nodes
  • N1a: 1 metastatic lymph node
  • N1b: 2-3 positive lymph nodes
  • N1c: Small deposits of tumor in pericolic /rectal tissue not apparently in or developed in lymph node
  • N2a: 4-6 positive lymph nodes
  • N2b: 7 or more positive lymph nodes 

Distant metastases (M)

  • M0: No distant metastases
  • M1: Distant metastases present

The stage of the cancer - TNM classification

The extension (stage) of the cancer should be assessed before start of the treatment. This is called clinical stage cTNM. cTNM is based on cT (clinically evaluated T), cN (clinically evaluated lymph node), cM (clinically evaluated distant metastases). TNM stage is also commonly named by separate examination, for instance MR based = mT, mN.

cTNM is based on all available information from:

  • Clinical examination
  • Endoscopy
  • Radiology

The final stage is given after the evaluation of the pathology specimen, and is given prefix “p”. Pathological TNM (pTNM) is based on pT, pN and the apprehension of M (operation/ radiology).

If the patient has received neoadjuvant treatment, this may have changed the size and grade of infiltration of the tumor and also extent of lymph node metastases. The pathology TNM can therefore vary from the cTNM before the treatment started. Pathology stage after neoadjuvant treatment shall therefore be given as yTNM. yTNM, pathology stage after neoadjuvant treatment is based on yT and yN.

The final stage is based on pT, pN and M. In ordinary routine only 5 stages are applied. The table below shows the TNM (UICC/AJCC) and Dukes' stages.

TNM (UICC/AJCC) stages and Dukes' stages

UICC-stage T N M Dukes
0 Tis N0 M0 0
I T1, T2 N0 M0 A
II
T3, T4
N0 M0 B
III
Any T
N1-2 M0 C
IV Any T Any N M1 D

Stratification according to these 5 categories achieves inaccurate prognostic groups. For better comparable groups staging into 10 subgroups is available.

TNM (UICC/AJCC) stages and Dukes' stages

UICC-stages T N M Dukes
0 Tis N0 M0 0
I T1, T2 N0 M0 A
II A T3 N0 M0 B
II B T4a N0 M0 B
II C
T4b N0 M0 B
III A

T1-T2

T1, T2

N1

N2a

M0

M0

C
III B

T3, T4a

T2, T3

T1, T2

N1

N2a

N2b

M

M0

M0

C
III C

T4a

T2, T4a

T4b

N2a

N2b

N1, N2

M0 C
IV A
Any T Any N
M1a D
IV B
Any T
Any N
M1b D

Classification according to oncological treatment effect

The treatment effect after chemoradiation is evaluated by Tumor Regression Grading (TRG), which involves assessment of the relative amount of tumor cells and desmoplastic reaction (fibrosis). Classification systems applies 3- or 5- subgroups.

Example of 5-part TRG-graded surgical specimens (19) (click to enlarge images)

Grade 1

Complete tumor regression. No tumor cells evident, only fibrosis.

Grade 2

Tumor cells spread in fibrosis.

Grade 3

Increased number of tumor cells, but still fibrosis dominating the image.

Grade 4

Tumor cells dominating.
Little fibrosis.

Grade 5

Well maintained tumor tissue. No fibrosis.

 

Classification of residual tumor (R-stage)

This classification is based on x-ray examination before/ during the operation, the surgical peroperative findings and the pathology examination of the resected specimen.

  • R0 – No known distant metastases, no local remaining tumor identified by the surgeon preoperatively, no microscopic tumor remains after surgery.
  • R1 – Microscopic tumor in the resection margin of within 1 mm from this (=circumpherential resection margin < 1 mm) and no further known remaining tumor.
  • R2 – Macroscopic tumor remains locally (identified by the surgeon) or distant metastases not resected.

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