A nodal positivity constant: new perspectives in lymph node evaluation and colorectal cancer.

Purpose: To date, associations between the number of lymph nodes evaluated, staging, and survival have been examined in the context of large population-based studies conducted by a small number of investigators. Therefore, although high-quality data are available, perspective is lacking.

Methods: Studies for this paper were identified by searches of Medline, Scopus, PubMed, and manual searching of references from articles, using the search terms ''colorectal cancer'', ''nodal status'' and ''lymph node''.

Results: It is clear that survival benefit increases with the increasing number of lymph nodes harvested. Despite this observation, there has been no significant increase in the proportion of node-positive cancers over the past two decades.

Conclusion: The nodal positivity rate for colorectal cancer consistently approximates 40 % across a wide range of studies internationally, a phenomenon that has not previously been recognized in the literature. We review the evidence and introduce the concept of a nodal positivity constant.