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Washington University Experience | NEOPLASMS (EMBRYONAL) | Medulloblastoma, Histologically Defined | Large cell-Anaplastic (LCA) | 4D Medulloblastoma, LCA (Case 4) GFAP
Reactivity for GFAP is identified in only rare tumor cells, as well as in reactive astrocytes and uninvolved neuropil. ---- Not shown: Uniformly strong nuclear reactivity for BAF47 (INI1) is present throughout the tissue, consistent with retained expression, effectively ruling out a diagnosis of atypical teratoid/rhabdoid tumor. ---- Heterozygosity on chromosome 17p and MYC amplification are prognostic indicators in medulloblastomas. FISH studies were performed to evaluate this tumor for the presence of isochromosome 17q and for amplification of c-myc (using fluorescent probes for the centromere of chromosome 17 [17cen] and the NF-1 locus on the long arm of chromosome 17 [17q11.2], and probes for the centromere of chromosome 8 [8cen] and C-MYC locus 8q24.12-q24.13, respectively). In this case, extra NF1 signals in comparison to the centromere 17 were observed often with one pair of signals in close proximity to each other; this pattern is consistent with isochromosome 17q formation. Focal amplification of c-myc and polysomies (gains) of chromosomes 8 and 17 were also identified.
