Aim
The majority of patients with pT2 colon cancer have no lymph node metastasis (LNM). Knowledge of risk factors for LNM in pT2 colon cancer could identify patients at low risk and thereby potential candidates for local tumour excision. The aim of this work was to identify risk factors for LNM in pT2 colon cancer and describe a subgroup of low-risk patients.

Method
This is a retrospective cohort study of patients with pT2 colon cancer from a nationwide Danish colorectal cancer database. Age, tumour size, location, histological type, mismatch repair protein status and venous, lymphatic and perineural invasion were included as potential risk factors in multivariate analysis. The primary outcome was LNM.

Results
We identified 1306 patients with pT2 colon cancer. LNM was present in 244 (19%). Demographic data were comparable in patients with and without LNM, and 864 patients who had complete histological data were included for multivariate analysis. Lymphatic (OR = 3.60, 95% CI 2.14–5.9), venous (OR = 1.70, 95% CI 1.03–2.74) and perineural (OR = 4.61, 95% CI 1.60–13.5) invasion were independent risk factors for LNM. Patients with deficient mismatch repair protein tumours had a decreased risk of LNM (OR = 0.55, 95% CI 0.31–0.95). Patients with clinical Stage I colon cancer and without risk factors had a 10.5% (47/443) risk of LNM. For patients with tumours with deficient mismatch repair protein status and no risk factors, the risk was 7.9%.

Conclusion
Lymphatic, venous and perineural invasion are significant risk factors for LNM, and we identified a subgroup of patients with a low risk of LNM.