The major biallelic inactivation of BRCA1 and/or BRCA2 in uLMS, which is one of the most proficient biomarkers for the response of poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitors, is somatic homozygous deletion of BRCA2, although germline pathogenic or likely pathogenic mutations, along with loss of heterozygosity (LOH), are major causes of biallelic inactivation of BRCA1/2 in other gynecologic malignancies, including ovarian cancer [49]. This evidence concerns the gene BRCA1 and ovarian cancer.