A 68-year-old female patient with tenesmus and blood in the stool was admitted to the S.G. Moscati Hospital of Taranto. Investigations revealed infiltrative mucinous colon adenocarcinoma accompanied by lymph node metastases. Following surgery and adjuvant chemotherapy, computed tomography (CT) and carcinoembryonic antigen screening were negative. Two years later, CT demonstrated a liver lesion. Histologic and genetic analyses confirmed the diagnosis of metastatic colorectal cancer with the coexistence ofKRASandBRAFmutations in hepatic metastases and the presence of theBRAFV600E in the primary tumour. It is unclear whether the lack of response was due toBRAFmutations, but the data suggest that mutatedBRAFconfers resistance to anti-epidermal growth factor receptor therapy. In our patient,BRAFmutation turned out to be a negative prognostic factor, and it may have been the cause of clinical implications for disease progression and therapeutic responses
