Cytogenetic evaluation of isochromosome 17q in posterior fossa tumors of children and correlation with clinical outcome in medulloblastoma. Detection of a novel chromosomal abnormality.
BACKGROUND
A number of chromosomal abnormalities have been described in the presence of central nervous system tumors; isochromosome 17q, representing a loss of heterozygosity for the short arm of the chromosome 17, is the one most frequently reported in association with medulloblastoma. The purpose of this study was to evaluate the prognostic correlation of this variable, compared with other variables (surgery extent and radiotherapy), with survival.


RESULTS
We looked for the presence of i(17q) in 32 children affected by posterior fossa tumors, including 16 medulloblastomas and 2 teratoid/rhabdoid tumors. For our study we used both karyotypic analysis and the fluorescence in situ hybridization (FISH) procedure, both on fresh and on paraffin-embedded tissues. Cytogenetic analysis allowed us to detect a hitherto unreported abnormality in medulloblastoma: ins(1;10)(q31;q23q26). Moreover, 16 of the 32 patients analyzed by FISH were found to be positive for the presence of i(17q): the 2 with teratoid/rhabdoid tumors, 11 of 16 with medulloblastomas, plus 1 with ependymoblastoma and 2 with anaplastic astrocytomas. As far as the outcome of medulloblastoma patients is concerned, we found that 8 out of the 10 children whose tumor had been totally removed had a favorable outcome regardless of the presence of i(17q): 4 were i(17q) positive and 4 i(17q) negative.


CONCLUSIONS
Although it was impossible to draw any definitive conclusion about detection of i(17q) in central nervous system tumors in infancy, particularly in the case of medulloblastoma, we suggest that this chromosomal abnormality is not an independent prognostic factor, but may be a marker for uncontrolled cell proliferation.
DeChiara
Carolina
C
Department of Pediatrics, Faculty of Medicine, University Federico II of Naples, Via S. Pansini, 5, 80131 Naples, Italy.
Borghese
Annamaria
A
Fiorillo
Amedeo
A
Genesio
Rita
R
Conti
Anna
A
D'Amore
Rosa
R
Pettinato
Guido
G
Varone
Antonio
A
Maggi
Giuseppe
G
D002528:Cerebellar Neoplasms / Q000235:genetics* / Q000473:pathology; D002648:Child; D002675:Child, Preschool; D002869:Chromosome Aberrations; D002886:Chromosomes, Human, Pair 17 / Q000235:genetics*; D003582:Cytogenetics / Q000379:methods; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007223:Infant; D015192:Infratentorial Neoplasms / Q000235:genetics* / Q000473:pathology; D007399:Interphase / Q000235:genetics; D018404:Isochromosomes / Q000235:genetics*; D007621:Karyotyping; D008297:Male; D008527:Medulloblastoma / Q000235:genetics* / Q000473:pathology; D011379:Prognosis; D014407:Tumor Cells, Cultured