ISOCHROMOSOME 17Q DEMONSTRATED BY INTERPHASE FLUORESCENCE IN-SITU HYBRIDIZATION IN PRIMITIVE NEUROECTODERMAL TUMORS OF THE CENTRAL-NERVOUS-SYSTEM

We previously reported an i(17q) as a non-random finding in childhood primitive neuroectodermal tumors (PNETs) of the central nervous system . In the present study, we describe a two-color interphase fluorescenc e in situ hybridization (FISH) assay for detection of chromosome 17 ab normalities in tumors. Thirty-four PNETs were analyzed by FISH with a series of chromosome 17-specific probes which map to 17p13.3-17q25. Th e results from the FISH assay were then compared to the karyotypes pre pared from the tumors. Ten of the 34 cases demonstrated an i(17q) by F ISH and standard cytogenetics. Two PNETs were shown to have an it i(17 q) by FISH alone, and three additional tumors had deletions of 17p. Th us, a total of 15 of 34 (44%) of the PNETs in this series had a deleti on of 17p. This study confirms and extends our previous reports that a n i(17q) is the most common cytogenetic abnormality in PNETs. The inte rphase FISH assay which we employed will have clinical utility for dia gnosis of children with malignant brain tumors, and it may be used for identification of tumors with 17p deletions for molecular studies aim ed at identifying disease genes. (C) 1995 Wiley-Liss, Inc.