RB1 and neoplasm: In addition to the childhood tumour retinoblastoma, RB1 inactivation has also been demonstrated in a variety of tumours including sarcomas, lung, breast, and bladder carcinomas, as well as malignant gliomas (Cance et al, 1990; Xu et al, 1991; Logothetis et al, 1992; Trudel et al, 1992; Ichimura et al, 1996; Tsuzuki et al, 1996; Ueki et al, 1996).