Challenging the extended phenotype: HRD-negative salivary gland carcinoma in a BRCA1 founder-variant carrier, case report and literature review

This represents the first SGT in a <i>BRCA1</i> carrier evaluated with HRD testing. The absence of HRD argues against BRCA1-driven tumorigenesis despite clear familial segregation. These findings challenge the presumed causal relationship between BRCA1 variants and SGT development. Clinical implications are direct: SGTs in <i>BRCA1</i> carriers should not be assumed eligible for PARP inhibitor therapy without HRD confirmation, and enhanced surveillance appears unwarranted. This case underscores that co-occurrence does not establish causation and highlights the critical importance of functional validation before expanding hereditary cancer spectra.