RB1 and retinoblastoma: Hansen et al. (1985) and Dryja et al. (1986) subsequently demonstrated that osteosarcoma—one of the common second primary cancers to affect patients who carry a pathogenic variant in RB1—also showed somatic loss of heterozygosity in the region of chromosome 13 that contains the RB1 locus in patients both with and without retinoblastoma.