BRCA1 encodes a large nuclear protein that helps maintain genomic stability by coordinating the repair of DNA double-strand breaks through homologous recombination, and it also regulates transcription and the cell cycle. It acts as a tumor suppressor, working with proteins such as RAD51, BRCA2, BARD1, and PALB2 to preserve genome integrity. Inherited alterations in BRCA1 cause hereditary breast and ovarian cancer syndrome, with elevated risks of breast, ovarian, prostate, and pancreatic cancers, and biallelic loss underlies a rare form of Fanconi anemia. Because BRCA1-driven tumors rely on impaired DNA repair, they are treatable with PARP inhibitors.

BRCA1 is a tumor suppressor essential for DNA double-strand break repair, and loss-of-function variants are the established mechanism behind hereditary breast and ovarian cancer risk. This variant creates a premature stop codon predicted to eliminate functional protein through nonsense-mediated decay, consistent with that established disease mechanism, and its complete absence from population databases further supports pathogenic potential, together supporting a Likely Pathogenic classification.