Comparative genomic hybridization and histological variation in primitive neuroectodermal tumours

The objective of this study was to test the hypothesis that chromosomal imb alances in central nervous system primitive neuroectodermal tumours (PNETs) reflect site and histology. We used comparative genomic hybridization to s tudy 37 cases of PNET, of which four were cerebral and 31 were medulloblast omas classified histologically as classic (n = 17) or nodular/desmoplastic (n = 14). Tumour immunophenotype was characterized with antibodies to neuro glial, mesenchymal and epithelial markers, Chromosomal imbalances were dete cted in 28 medulloblastomas (90%), and significant associations between tum our variants and genetic abnormalities were demonstrated. Aberrations sugge sting isochromosome 17q were present in eight (26%) medulloblastomas, of wh ich seven were classic variants. None of these cases, or a further six with gain of 17q, showed immunoreactivity for glial fibrillary acidic protein, Loss on 9q was found in six cases (19%), five of them nodular/desmoplastic. Loss of 22 occurred in four (13%), all classic medulloblastomas in young p atients with a poor outcome and immunoreactivity for more than one epitheli al or mesenchymal marker. Different patterns of imbalance were found in the cerebral PNETs. There were no abnormalities of chromosome 17, but all thre e cases with imbalance showed losses of 3p12.3-p14.