Hecht et al. (1995) studied a large multigenerational family with multiple exostoses and, in 1 member, a chondrosarcoma. The family demonstrated linkage of the disease to chromosome 11 markers. Loss of marker D11S903 was observed in constitutional DNA ... Hecht et al. (1995) studied a large multigenerational family with multiple exostoses and, in 1 member, a chondrosarcoma. The family demonstrated linkage of the disease to chromosome 11 markers. Loss of marker D11S903 was observed in constitutional DNA from all affected individuals and in the tumor sample. In further studies of constitutional and chondrosarcoma DNA from 6 unrelated individuals, 2 of whom had multiple exostoses, 1 tumor from an individual with multiple exostoses showed LOH for chromosome 8 markers in the region where the EXT1 gene maps (8q24.1), and a person with a sporadic chondrosarcoma was found to have a tumor-specific LOH and a homozygous deletion of chromosome 11 markers from the pericentric region, where the EXT2 gene maps. These findings suggested to Hecht et al. (1995) that EXT genes may be tumor suppressor genes and that the initiation of tumor development may follow a multistep model.