[Tumour deposition (TD), a probably underestimated poor prognostic criterion, to be taken into account in the therapeutic management of patients with stage III colon cancer]

The management of colorectal cancer (CRC) relies heavily on TNM staging. In order to improve this staging, it is essential to identify all histological markers bearing a significant prognostic value. Among these, tumor deposits (TDs), defined as tumor foci in the pericolonic or perirectal adipose tissue with no residual lymph node tissue, have been shown to be associated with poor prognosis in cohort studies leading to their individualization in the TNM7 classification as pN1c. However, TDs are only considered in the absence of lymph node metastases. There is no consensus on this particular way of integrating TDs in the TNM classification. Indeed, at the time when the choice of the type of adjuvant treatment and its duration in stage III colon cancers (i.e. with lymph node metastases) is based on pT and pN criteria, taking into account TDs only in the absence of concomitant lymph node metastases is potentially responsible for a misclassification of some patients and wrong therapeutic decisions. In addition, many questions concerning the true definition of TDs, their origin, their prognostic value and the optimization of their consideration remain open. The objective of this review is to provide a synthesis of current knowledge on TDs in CRC, in view of their prognostic importance, their biological complexity and the scientific interest they are currently the subject of.