KRAS and cancer: In MSS tumors, the most frequently mutated known cancer genes were TP53 (44/91, 48%), KRAS (43/91, 47%), APC (20/91, 22%), SMAD4 (14/91, 15%), SOX9 (11/91, 12%), BRAF (10/91, 11%), and ERBB2 (10/91, 11%).