BRCA germline mutations are the most common predisposing factor in familial breast-ovarian cancer syndrome families. However, many screened patients are identified as harboring BRCA variants of uncertain significance (VUS), rather than carrying deleterious germline mutations [Calo et al.: Cancers 2010; 2:1644-1660]. While such VUSs are typically reclassified as benign polymorphisms, this may occur years after the VUS is first identified [Murray et al.: Genet Med 2011; 13; 998-1005]. Loss of heterozygosity (LOH) of BRCA is nearly always the gatekeeper event in inherited BRCA-related breast cancer and LOH of BRCA is rare in sporadic cancers [Osorio et al.: Int J Cancer 2002; 99:305-309]. Here, we describe a patient identified as carrying a germline BRCA VUS. Tumor next-generation sequencing (NGS) demonstrated a very high mutation allelic frequency for that BRCA VUS, consistent with LOH. This case illustrates that since BRCA LOH is the typical mechanism of transformation in inherited BRCA-related breast cancers, NGS might be used to suggest that the BRCA VUS is actually cancer predisposing in a particular family. As a result, this may help patients make more informed decisions regarding screening and prophylactic therapy, long before official reclassification of the VUS occurs.
Keywords: BRCA variant; Next-generation sequencing; Variant of uncertain significance.