Table 2.
Major changes in the last 4 editions of TNM classification for colorectal cancer.
| Edition (year) | T category | N category | M category | Stage grouping |
|---|---|---|---|---|
| 4th (1987) | — | Introducing N3 category | — | — |
|
| ||||
| 5th (1997) | — | Removing N3 category | — | — |
| TDs: introducing the 3 mm rule | — | |||
|
| ||||
| 6th (2002) | TDs: replacing the 3 mm rule with the contour rule | — | Subdividing stage III into IIIA, IIIB, and IIIC | |
| T4 split into T4a and T4b | ITC considered as N0 | |||
|
| ||||
| 7th (2009) | Changes in TD classification | M1 split into M1a and M1b | Subdividing stage IV into IVA and IVB | |
| — | Subdividing N1 into N1a, N1b, and N1c and N2 into N2a and N2b | |||
ITC, isolated tumour cells.