Systematic review and meta-analysis of histopathological factors influencing the risk of lymph node metastasis in early colorectal cancer.

Aim: Lymph node (LN) metastases are present in up to 17% of early colorectal cancers (pT1). Identification of associated histopathological factors would enable counselling of patients regarding this risk.

Method: Pubmed and Embase were employed utilizing the terms 'early colorectal cancer', 'lymph node metastasis', 'submucosal invasion', 'lymphovascular invasion', 'tumour budding' and 'histological differentiation'. Analysis was performed using REVIEW MANAGER 5.1.

Results: Twenty-three cohort studies including 4510 patients were analysed. There was a significantly higher risk of LN metastasis with a depth of submucosal invasion > 1 mm than with lesser degrees of penetration (OR 3.87, 95% CI 1.50-10.00, P = 0.005). Lymphovascular invasion was significantly associated with LN metastasis (OR 4.81, 95% CI 3.14-7.37, P < 0.00001). Poorly differentiated tumours had a higher risk of LN metastasis compared with well or moderately differentiated tumours (OR 5.60, 95% CI 2.90-10.82, P < 0.00001). Tumour budding was found to be significantly associated with LN metastasis (OR 7.74, 95% CI 4.47-13.39, P < 0.001).

Conclusion: Meta-analysis of the current literature demonstrates that in early colorectal cancer a depth of submucosal invasion by the primary tumour of > 1 mm, lymphovascular invasion, poor differentiation and tumour budding are significantly associated with LN metastasis.