The most common current staging system is the TNM (for tumors/nodes/metastases) system, though many doctors still use the older Dukes system. The TNM system assigns a number^[31]:

• T - The degree of invasion of the intestinal wall
  • T0 - no evidence of tumor
  • Tis- cancer in situ (tumor present, but no invasion)
  • T1 - invasion through muscularis mucosa into submucosa
  • T2 - invasion through submucosa into the muscularis propria (i.e. proper muscle of the bowel wall)
  • T3 - invasion through the muscularis propria into subserosa but not to any neighbouring organs or tissues
  • T4 - invasion of surrounding structures (e.g. bladder) or with tumour cells on the free external surface of the bowel
• N - the degree of lymphatic node involvement
  • N0 - no lymph nodes involved
  • N1 - one to three nodes involved
  • N2 - four or more nodes involved
• M - the degree of metastasis
  • M0 - no metastasis
  • M1 - metastasis present