Colorectal cancer staging using TNM 7: is it time to use this new staging system?

The authors audited pathological colorectal cancer staging according to tumour node metastasis (TNM) 7 and using TNM 5 as a gold standard. 144 consecutive colorectal cancer resection specimens were staged prospectively using both TNM 5 and TNM 7 criteria during routine reporting by specialist gastrointestinal pathologists within a single institution. The pN stage remained the same under both systems apart from the required subclassification of pN1 and pN2 under TNM 7. The TNM 7 pN1c category was used in only 3% of cases. All cases staged as pT4 underwent reversal of pT4 subclassification using TNM 7 compared with TNM 5. A previous study revealed stage migration from pN1 to pN2 in 32.6% of cases under TNM 7 compared with TNM 5. The difference in frequency of pN stage migration between this study and our audit suggests that the application of TNM 7 to the assessment of discontinuous/satellite tumour foci is subject to significant inter-observer variability.