Comparative Genomic Hybridization Detects An Increased Number of Chromosomal Alterations in Large Cell/Anaplastic Medulloblastomas

We correlate chromosomal changes in medulloblastomas with histologic subtype, reporting the analysis of 33 medulloblastoma specimens by comparative genomic hybridization, and a subset by fluorescence in situ hybridization. Of the 33 tumors, 5 were desmoplastic/nodular, 10 were histologically classic, and 18 were large cell/anaplastic. Chromosomal gains and losses were more common in anaplastic medulloblastomas than in non‐anaplastic ones. We identified 4 medulloblastomas with c‐myc amplification and 5 medulloblastomas with N‐myc amplification; all 9 were of the large cell/anaplastic subtype. Additional regions with high level gains included 2q14‐22, 3p23, 5p14‐pter, 8q24, 9p22‐23, 10p12‐pter, 12q24, 12p11‐12, 17p11‐12, and Xp11. The majority of these high level gains occurred in anaplastic cases. We also found loss of chromosome 17p in 7 large cell/anaplastic cases but no non‐anaplastic medulloblastomas. Finally, we detected a significantly increased overall number of chromosomal alterations in large cell/anaplastic medulloblastomas (6.8/case) compared to non‐anaplastic ones (3.3/case). These findings support an association between myc oncogene amplification, 17p loss, and large cell/anaplastic histology.