The aim of this review is to discuss the emerging role of mast cells (MCs), microRNAs (miRNAs), KRAS and v-raf murine sarcoma viral oncogene homologue B (BRAF) as diagnostic and prognostic biomarkers for CRC, evaluating their influence as potential therapy targets in the forthcoming era of precision medicine. The gene discussed is KRAS; the disease is colorectal carcinoma.