Rb defects are relatively prevalent in TNBC, but are not unique to this cancer subtype and are also evident in in many tumour types, including, for example, small-cell lung cancers, bladder carcinomas, osteosarcomas, glioblastomas, endometrial carcinomas and retinoblastomas [7, 8, 57–59]. This evidence concerns the gene RB1 and osteosarcoma.