Primary tumour location (right sided versus left sided) has recently emerged as prognostic and predictive factor in patients with KRAS wild type mCRC treated with chemotherapy and EGFR directed antibodies, with worse survival in patients with right sided colon cancer and KRAS wild type [10, 11], whilst KRAS mutations have been associated with worse survival only in left sided cancer [12]. The gene discussed is KRAS; the disease is neoplasm.