BRCA1 and cancer: Supporting this evidence is the observation that, although loss of heterozygosity (LOH) in somatic cells is considered essential for tumorigenesis in cancers harboring dysfunctional BRCA1/2, germline heterozygous BRCA2 mutations appear to suffice for carcinogenesis in several tissues, with LOH either absent or occurring relatively late in cancer progression [(62) and refs therein].