Backgrounds: Breast cancer belongs to the most serious malignant diseases in the female population in the Czech Republic. It is assumed that inherited mutations contribute to the development of 5-10% of cancers. In recent years, the role of mutations of the low penetrance genes is studied intensively. One of them is checkpoint kinase 2 (CHEK2). Mutations in this gene were shown to predispose to the development of se veral inherited cancer sy ndromes, including breast cancer. Study design: We háve performed mutation analysis of pathogenic CHEK2 allele cl lOOdelC in 1776 subjects including 688 breast cancer patients, 358 patients screened for mutations in major predisposing genes and 730 non cancer controls. Mutation analysis was based on DHPLC prescreening, mutations were confirmed by sequencing. Results: We háve found 6 mutation carriers: 3 in sporadic breast cancer patients' cohort, one male breast cancer patient in hereditary breast cancer patients' cohort and 2 among 730 controls. Conclusion: Based on our data, we can speculate that Czech Republic belongs to the countries with low occur-rence of CHEK2 cllOOdelC allele, which limits clinical utilization of CHEK2 genetic analysis.

        Key words: breast cancer, CHEK2, hereditary disposition, germline mutation