GENETIC INSTABILITY IN NERVE SHEATH CELL TUMORS

After in vitro culture, we analyzed cytogenetically four acoustic nerv e neurinomas, one intraspinal neurinoma and one neurofibroma obtained from unrelated patients. Monosomy of chromosomes 22 and 16 was an abno rmality common to all cases, followed in frequency by loss of chromoso mes 18 (three cases) and chromosomes 8, 17 and 19 (two cases). Trisomy of chromosome 20 was also detected in two cases. Structural rearrange ments were detected at low frequencies, with del(10)(p12) being presen t in two cases. In addition, we observed cell subpopulations showing a certain degree of genetic instability, reflected by the presence of p olyploid cells with inconsistent abnormalities, endoreduplications and telomeric associations resulting in dicentric chromosomes. It is prob able that these cytogenetic abnormalities represent some kind of evolu tionary advantage for the in vitro progression of nerve sheath tumors.