OBJECTIVETo investigate genomic DNA imbalances in ependymomas (EDMs) and their correlations with the tumor histological types, grades, locations, patients' gender and age.

METHODSChromosomal gains and losses in 16 cases of EDM were analyzed using comparative genomic hybridization.

RESULTSChromosomal regional gain and loss were found in 15 and 13 of 16 EDM cases respectively including totally 24 regional gains and 19 regional losses in all the tumors studied. Both regional gains and losses were mostly seen in myxopapillary EDMs (MPE, WHO grade I), more commonly seen in cellular EDMs (CE, WHO grade II) and tanycytic EDMs (TE, WHO grade II) than in anaplastic EDMs (AE, WHO grade III). Some of the regional gains and losses appeared only in one subtype of MPE, CE, TE and AE cases resulting in development of specific imbalance profiles of certain subtype in these cases. MPE, CE and TE often had +7. Chromosomal +5 occurred only in MPE and CE, and -22q was only seen in CE and TE. AE frequently had +1q, but none had +5, +7, -4q, -19q and -22q. The frequencies of any regional gain or loss were not affected by patients' genders (P > 0.05). Chromosomal +1q and +7p happened predominantly in intracranial EDMs with an averagely onset age of

CONCLUSIONSThe frequencies of chromosomal imbalances in EDMs decrease as the tumor grade increases. Characteristic chromosomal imbalances in each subtype may play an important role in determination of histological phenotypes and tumor grades. Chromosomal +1q, +5, +7p, +7, -4q, -19q and -22q are alterations which may dictate the biological behaviors of these tumors and the patients' prognosis.