Giordana M T, Migheli A, Pavanelli E
Department of Neurosciences, University of Turin, Italy.
Neuropathol Appl Neurobiol. 1998 Jun;24(3):233-8. doi: 10.1046/j.1365-2990.1998.00102.x.
Isochromosome 17q (i[17q]) is the most frequent chromosomal abnormality in medulloblastoma, occurring in 30-60% of cases by karyotype analysis. In the present study i[17q] was demonstrated in routinely processed tissue sections of 20 medulloblastomas by in situ hybridization (ISH), using a chromosome 17 centromeric alpha satellite DNA probe. All medulloblastomas showed the i[17q] specific signal, i.e. two hybridization spots slightly apart from each other. The specific hybridization signal was not observed in ependymomas, cerebellar astrocytomas, haemangioblastomas, supratentorial neuroblastomas and ependymoblastomas. The constant finding of i[17q] in medulloblastoma depends on the much higher number of nuclei which can be analysed by ISH compared with cytogenetic techniques. Molecular data on medulloblastoma are consistent with the present results. The number of cells with i[17q] in medulloblastoma cases ranged from 3% to 9%; these figures are underestimated because of nuclear truncation in tissue sections. The percentage was not linked to patients' age, location of tumour, MIB-1 labelling index and histological type (classical vs desmoplastic). The present results indicate that i[17q] is a key event in the pathogenesis of medulloblastoma, and suggest a genetic difference between medulloblastoma and other primitive neuroectodermal tumours.
17号染色体等臂染色体（i[17q]）是髓母细胞瘤中最常见的染色体异常，通过核型分析在30%-60%的病例中出现。在本研究中，使用17号染色体着丝粒α卫星DNA探针，通过原位杂交（ISH）在20例髓母细胞瘤的常规处理组织切片中证实了i[17q]。所有髓母细胞瘤均显示i[17q]特异性信号，即两个彼此稍有间隔的杂交点。在室管膜瘤、小脑星形细胞瘤、血管母细胞瘤、幕上神经母细胞瘤和室管膜母细胞瘤中未观察到特异性杂交信号。髓母细胞瘤中i[17q]的持续发现取决于与细胞遗传学技术相比，ISH可分析的细胞核数量要多得多。关于髓母细胞瘤的分子数据与目前的结果一致。髓母细胞瘤病例中具有i[17q]的细胞数量在3%至9%之间；由于组织切片中的细胞核截断，这些数字被低估了。该百分比与患者年龄、肿瘤位置、MIB-1标记指数和组织学类型（经典型与促纤维增生型）无关。目前的结果表明，i[17q]是髓母细胞瘤发病机制中的关键事件，并提示髓母细胞瘤与其他原始神经外胚层肿瘤之间存在遗传差异。
