[Pathological Diagnosis and Its Molecular Basis in Colorectal Cancer]

The genomic instability in colon cancer can be divided into at least 2 major types: chromosomal instability (CIN) and microsatellite instability(MSI). Although there are some overlaps between the 2 types, these are thought to be mutually exclusive. Colorectal tumors progress through a series of histopathologic grades, ranging from dysplastic crypts through small benign tumors to malignant cancers. This progression is the result of a series of genetic changes that involve activation of oncogenes and inactivation of tumor suppressor genes, ie, the CIN pathway. In contrast, MSI develops as a result of epigenetic silencing of MLH1 in sporadic tumors-in a background of methylation of CpG islands in gene promoters-and in tumors that frequently show BRAF mutation. Several tumor prognostic factors have been identified for colorectal cancer, including, tumor budding and molecular factors. In this review, we discuss the genetic mechanisms of colorectal cancer and the relationship of these alterations with emerging biomarkers for pathological diagnosis, patient prognosis, and the prediction of treatment responses.