CHROMOSOMAL CHARACTERISTICS OF CHILDHOOD BRAIN-TUMORS

In the present cytogenetic analysis of 116 pediatric brain tumors, chr omosomal abnormalities were demonstrated in 44 cases, 48 cases reveale d only 46,XX or 46,XY cells, and 24 cases were nonproductive. In contr ast to studies of adult brain tumors in which isolated loss of one X o r the Y chromosome is often encountered, 45,X, -X and 45,X, -Y stemlin es or sidelines were not observed in this series of childhood tumors. Among the 27 medulloblastomas with cytogenetic abnormalities, chromoso me 1 was most frequently affected by structural deviations; the most p revalent specific alteration (7 of 2 7 tumors) was loss of 17p, throug h ill i(17)(q10) or unbalanced translocation. The majority of low grad e astrocytomas had normal stemlines, although one pilocytic astrocytom a and one cerebellar astrocytoma had frequent telomeric associations a nd a second pilocytic astrocytoma had a clone with trisomy II. Thirtee n of 19 high-grade and recurrent astrocytic tumors herd abnormal steml ines that were approximately equally divided among cases with chromoso mal counts in the near-diploid, hyperdiploid, and near-triploid-tetrap loid ranges. Although no consistent abnormalities were observed, subse ts of cases had structural abnormalities of chromosome 3, 7q, 9p, or 2 7p. The cases of childhood brain tumors described here demonstrate tha t 4s,X, -X, and 45,X, -Y stemlines or sidelines are rare in these tumo rs and confirm frequent loss of 17p in medulloblastomas. High-grade as trocytic tumors in children frequently have abnormal stemlines, often in the hyperdiploid and polyploid ranges, and they differ from high-gr ade gliomas in the adult by lacking consistent numerical and structura l deviations. (C) Elsevier Science Inc., 1997.