KRAS, NRAS, BRAF mutations and high counts of poorly differentiated clusters of neoplastic cells in colorectal cancer: observational analysis of 175 cases

A novel grading system based on the counting of poorly differentiated clusters (PDC) of neoplastic cells at the invasive margin and in the tumour stroma was recently introduced among the histological parameters predictive of adverse clinical outcome in colorectal cancer (CRC). The aim of this study was to correlate the histological grade based on PDC and the mutational status of KRAS, NRAS and BRAF genes in 175 consecutive CRCs. The highest PDC count under the objective lens of a ×20 microscopic field in each tumour was considered for grading assessment, so that PDC counts