Colon cancer staging is an estimate of the amount of penetration of a particular cancer. It is performed for diagnostic and research purposes, and to determine the best method of treatment. The systems for staging colorectal cancers depend on the extent of local invasion, the degree of lymph node involvement and whether there is distant metastasis.
Definitive staging can only be done after surgery has been performed and pathology reports reviewed. An exception to this principle would be after a colonoscopic polypectomy of a malignant pedunculated polyp with minimal invasion. Preoperative staging of rectal cancers may be done with endoscopic ultrasound. Adjunct staging of metastasis include Abdominal Ultrasound, MRI, CT, PET Scanning, and other imaging studies.
The most common staging system is the TNM (for tumors/nodes/metastases) system, from the American Joint Committee on Cancer (AJCC). The TNM system assigns a number based on three categories. "T" denotes the degree of invasion of the intestinal wall, "N" the degree of lymphatic node involvement, and "M" the degree of metastasis. The broader stage of a cancer is usually quoted as a number I, II, III, IV derived from the TNM value grouped by prognosis; a higher number indicates a more advanced cancer and likely a worse outcome. Details of this system are in the graph below:
| AJCC stage | TNM stage | 2002 6th edition TNM stage criteria for colorectal cancer (superceded by 2010 7th edition)[1] |
|---|---|---|
| Stage 0 | Tis N0 M0 | Tis: Tumor confined to mucosa; cancer-in-situ |
| Stage I | T1 N0 M0 | T1: Tumor invades submucosa |
| Stage I | T2 N0 M0 | T2: Tumor invades muscularis propria |
| Stage II-A | T3 N0 M0 | T3: Tumor invades subserosa or beyond (without other organs involved) |
| Stage II-B | T4 N0 M0 | T4: Tumor invades adjacent organs or perforates the visceral peritoneum |
| Stage III-A | T1-2 N1 M0 | N1: Metastasis to 1 to 3 regional lymph nodes. T1 or T2. |
| Stage III-B | T3-4 N1 M0 | N1: Metastasis to 1 to 3 regional lymph nodes. T3 or T4. |
| Stage III-C | any T, N2 M0 | N2: Metastasis to 4 or more regional lymph nodes. Any T. |
| Stage IV | any T, any N, M1 | M1: Distant metastases present. Any T, any N. |
Contents |
The Dukes classification is an older and less complicated staging system, that predates the TNM system. It identified the stages as:[2]
A: Tumor limited to mucosa; carcinoma in situ B1: Tumor grows through muscularis mucosae but not through muscularis propria B2: Tumor grows beyond muscularis propria C1: Stage B1 with regional lymph node metastases C2: Stage B2 with regional lymph node metastases D: Distant metastases.
venous invasion (v)
lymphatic invasion (l)
histologic grade (G)