Colorectal Cancer Classification Systems

The two most common classification systems are the Dukes and TNM (tumor/node/metastasis) systems. The original Dukes system was developed for classification of rectal cancers. Dukes A describes a rectal tumor that has not penetrated the wall and has no nodal involvement. Dukes B involves a penetrating cancer through the rectal wall but with no nodal involvement. Dukes C indicates lymph node involvement. The Dukes system was modified by Kirklin in 1949, extending the classification to include colon cancers. Turnbull in 1967 added Dukes D to describe metastases to distant organs. The Dukes classification fails to take into account the number of involved nodes and clinical factors, but it is still the single best predictor of survival.

The TNM system is based on the anatomic extent of the cancer. T stands for the extent of the primary tumor, N for the condition of the regional lymph nodes, and M for the presence or absence of distant metastases at the time of diagnosis.

The National Cancer Institute recently convened an expert panel to develop guidelines for colon and rectal surgery. As a result of this meeting, the panel recommended using the TNM system for tumor staging based on a review of the best available evidence.

{embed="cr/stat-menu-colon"}

Gregory L. Brotzman and Russell G. Robertson

{embed="cr/colon-ref"}