For example, our group was the first to describe HRRD in more than 80% of 121 osteosarcomas and our studies are broadly consistent in that HRRD exists in tumors that harbor chromosomal 13 deletions, either as bi‐chromosomal deletions that affect RB1 and BRCA2 genes equally or as single‐copy whole‐arm deletions of chromosome 13 that are complemented by focal deletions in BRCA2. This evidence concerns the gene RB1 and osteosarcoma.