Colorectal tumour deposits in the mesorectum and pericolon; a critical review

Although tumour deposits (TD) in the pericolic and mesorectal fat have been recognized since 1935, incorporation in the Tumour Node Metastasis (TNM)/American joint Committee on Cancer (AJCC) system took place in 1997. The 3-mm rule classified TD as lymph node metastases. This rule was changed in 2002, when the contour of the deposit became the diagnostic feature. This review has evaluated the 3714 patients described in the literature. The incidence of TD varies from 5 to 45%. Their origin has been shown to be heterogeneous; however, their presence indicates a poorer survival. The hazard ratio for death due to disease is 1.96. Various studies have tried to determine the importance of types of TD, based on contour, size and origin, but all fail to provide an evidence base to substantiate its use in the TNM system. To classify TD as positive lymph nodes after neoadjuvant therapy is a misconception, since the presence of tumour microfoci after therapy can be a sign of good response to treatment and indicative of a good prognosis. In conclusion, we did not find adequate evidence for the inclusion of TD in TNM/AJCC staging systems. Moreover, the current directives are confusing, and the definitions should not be used after neoadjuvant therapy.