BRCA1 and neoplasm: Importantly for the scope of this article, BRCA1 and BRCA2 are tumor-suppressor genes and, in accordance with Knudson’s two-hit model [11], the genotypes in tumors from mutation carriers typically show loss of heterozygosity (LOH), with preferential loss of the non-mutated or "wild-type" copy (wtLOH) of the gene, and its surrounding chromosomal region [12,13].