RESUMO
Background: KRAS oncogene is involved in colorectal carcinogenesis in 22 to 45% of cases. Aim: To determine the frequency, types and distribution of KRAS mutations in colorectal cancer. Material and Methods: KRAS mutations studies were carried out in primary tumors and metastases of colo-rectal cancer from 56 women aged 60 ± 14 years and 53 men aged 61 ± 11 years. Formalin fixed and paraffin embedded tissue samples were evaluated using RFLP (Restriction Fragment Length Polymorphism) and direct sequencing. Results: Primary tumors were located in the colon and rectum in 82 (75.2%) and 24 cases (20%), respectively. In three cases the extraction site of the tumor sample was unknown. In 46 cases (42.2%) KRAS mutations were demonstrated. The main point mutations were located in codon 12 (80.4%), G12D (39.1%), G12V (24.2%), G12S (6.5%), G12A (4.3%); G12C (4.3%), G12R (2.1%) and 19.6% at codon 13 (G13D). No differences were demonstrated in the frequency and distribution of mutations by gender, age, primary versus metastatic tumors or tumor location. Conclusions: In this series, 42% of colorectal cancer tissue samples had KRAS mutations. Their frequency and distribution are similar to those reported in the literature, except for G12C mutation.