Poorly Differentiated Clusters: Clinical Impact in Colorectal Cancer.

Colorectal cancer (CRC) is one of the most common malignancies worldwide and it still represents a major cause of cancer-related death. Postsurgical Tumor Node Metastasis (pTNM) stage is the main prognostic factor in CRC and it currently drives therapeutic protocols after surgery. However, CRC outcome is not always predictable on the basis of pTNM stage. Hence, there is the need to find additional prognostic factors that may allow to predict the clinical course of CRC regardless of pTNM stage, so that patients may receive the most appropriate treatment for their tumor. In recent years, the prognostic value of a novel grading system based on the counting of poorly differentiated clusters (PDCs) of neoplastic cells in tumor tissue was documented in CRC. In this article, we review the clinical relevance of grading based on PDC counting in CRC. In view of its high prognostic value and reproducibility, PDC grading could be introduced in routine histopathological report of CRC and used for therapeutic decision making. Although there is initial evidence that PDC may be correlated with biomolecular profile of CRC, whether their presence is associated with response to targeted therapies is still unknown and deserves further investigation.