Genetic characterisation of granular cell tumours.

Seven granular cell tumours (GCT) were studied by comparative genomic hybridisation. These consisted of two cerebral and one pituitary GCT as well as four other central nervous system tumours predominantly composed of granular cells (one glioblastoma, meningioma, ganglioglioma and neurinoma each). DNA copy number changes were found in four of seven tumours. Overall, losses (mean: 1.0 per tumour) were more frequent than gains (mean: 0.6 per tumour) and no high-level gains were found. The only DNA copy number change found in two tumours (both cerebral GCT) was loss of 13q21, while the other nine aberrations were only encountered once each: the granular cells of one cerebral GCT additionally showed +1p32-pter, +9q33-qter, +20q, -4, and -18q, of the glioblastoma +7 and -10, and of the meningioma -1p and -22q, while the pituitary GCT, the ganglioglioma and the neurinoma showed no imbalances. Our data suggest that a variety of genetic changes are associated with granular cell formation and support the notion that GCT are not a distinct tumour entity characterised by specific chromosomal imbalances but rather a degenerative phenomenon of cells of various origin showing DNA copy number changes akin to the underlying tumour.