The detection and role of lymphatic and blood vessel invasion in predicting survival in patients with node negative operable primary colorectal cancer.

Although vascular invasion in colorectal cancer has been recognised since 1938, detection methods and results remain inconsistent. Vascular invasion is currently an independent prognostic factor in colorectal cancer influencing disease progression and survival. The vascular system consists of three components, arterial, venous and lymphatic vessels, all of which can be invaded but accurate distinction between the components remains difficult with routine staining techniques. Even though higher detection rates with elastica staining, for large vessel invasion, and recent techniques for immunohistochemistry for small vessel invasion, have been reported, a standardised method of detection has not been agreed upon which is reflected in the variability of published results. As a result of the Bowel Cancer Screening Programme in the UK it will be necessary to attempt to identify and stratify patients better, to be able to handle the stage migration to early node negative colorectal cancer. At present up to a third of patients, with node-negative colorectal cancer on conventional histopathological analysis, ultimately die of recurrent disease. It is therefore important to develop and standardised methods to identify lymphatic and blood vessel invasion which will influence ultimate survival. The present review summarises the current status of detection methods for these components of vascular invasion.