The DNA samples in this study were derived from a primary tumor or metastasis,because the literature showed that mutations in KRAS, NRAS and BRAF are similar inboth types of samples15,20,29 and there is no disagreement in the statusof KRAS in different periods of patients evaluated, including at the time of theinitial diagnosis of the tumor and later in the course of the disease in themetastatic period and after cytotoxic chemotherapy. Here, NRAS is linked to neoplasm.