Are All Mutations the Same? A Rare Case Report of Coexisting Mutually Exclusive KRAS and BRAF Mutationsin a Patient with Metastatic Colon Adenocarcinoma

29-year-old Hispanic woman presented to the clinic with complaints of abdominal pain, nausea, fatigue, and constipation.Laboratory tests indicated the presence of iron deficiency anemia and transaminitis. Imaging evaluation revealed markedhepatomegaly with multiple hepatic metastases and pelvic lymphadenopathy. Biopsy of the hepatic lesions showed adenocarcinomapositive for pan-cytokeratin, CMA5.2, villin, and CDX2. She was positive for tumor markers CA 19-9, CA-125, and CEA. Uponfurther evaluation, she was found to have colorectal cancer positive for KRAS and BRAF mutations. Unfortunately, her diseaseprogressed rapidly and she expired within 3 months from the time of her first diagnosis. KRAS and BRAF mutations are rareenough to be considered virtually mutually exclusive but coexistent mutations appear to be a distinct molecular and clinical subsetwith aggressive course of illness, which is in dire need of new treatment strategies. Panitumumab and Cetuximab are approved forpatients with wild type KRAS CRC. Vemurafenib is a potent inhibitor of the kinase domain in mutant BRAF and its use in BRAFmutated colon cancer remains to be well established. Our report highlights the need to obtain tissue samples from these patientsfor analysis and to evaluate the benefit of Vemurafenib in colorectal cancers.