A New de novo BRCA1 Mutation in a Young Breast Cancer Patient: A Case Report.

Background: BRCA1 and BRCA2 genes represent the most investigated breast and ovarian cancer predisposition genes. Ten cases of pathogenic de novo BRCA1 variations and six cases of pathogenic de novo BRCA2 variation have been reported at present. Here, we report a new case of a de novo BRCA1 gene mutation. Case Presentation: A 30-year-old woman with no health issues and no family history for hereditary breast and ovarian cancer was diagnosed with a hormone receptor positive/HER2 negative invasive breast cancer. Genetic testing revealed a pathogenic variant in BRCA1 (c.4065_4068delTCAA) which was not found in her parents or sister. Conclusion: We report a new case of de novo BRCA1 mutation, confirmed by repeated germline testing of the index patient and her parents. The published BRCA1/2 de novo mutation rate is low. This is probably due - in part - to the strict testing criteria.