Table 1: Stage systems AJCC, Dukes, and Astler-Coller. AJCC system is the most used and precise staging system for CRC and combines three letters (T: for the primary tumour, N: for spread to lymph nodes, and M: for metastasis) and numbers from 0 to 4 (indicating more severity for a higher number).

AJCC/TNMDukesAstler-Coller

Stage 0Tis, N0, M0

Stage IT1-T2, N0, M0AA, B1

Stage IIAT3, N0, M0BB2

Stage IIBT4a, N0, M0BB2

Stage IICT4b, N0, M0BB3

Stage IIIAT1-T2, N1, M0 C C1
T1, N2a, M0

Stage IIIBT3-T4a, N1, M0 C C1, C2
T2-T3, N2a, M0
T1-T2, N2b, M0

Stage IIICT4a, N2a, M0 C C2, C3
T3-T4, N2b, M0
T4b, N1-N2, M0

Stage IVAny T, Any N, M1a D
Any T, Any N, M1b