Loss of 13q arm has been found in about 0–30% of solid tumours, including nervous system neoplasms in which up to 45% of GB display loss at the RB1 locus (Ishikawa et al, 1991; Hogg et al, 1993; Xu et al, 1993; Gouyer et al, 1994; Henson et al, 1994; Ichimura et al, 1996). The gene discussed is RB1; the disease is nervous system neoplasm.