In univariate analyses, rectal cancers showed an increased KRAS discordance rate when compared with colon cancers (28.6% vs. 13.9%; P = 0.047), and biopsied primary tumor specimens showed a trend for an increased discordant rate when compared with resected primary tumor specimens (40.0% vs. 15.8%; P = 0.073). This evidence concerns the gene KRAS and malignant colon neoplasm.