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Washington University Experience | NEOPLASMS (EMBRYONAL) | Medulloblastoma, Histologically Defined | Extensive Nodularity (MBEN) | 2G2 Medulloblastoma, focal nodularity (Case 2) b-catenin 5.jpg
Beta catenin immunoreactivity shows only cytoplasmic staining with no nuclear immunoreactivity. ---- Not shown: INI-1 is retained in nuclei, ruling out atypical teratoid rhabdoid tumor. p53 immunoreactivity labels very rare nuclei. FISH showed no evidence of NMYC or CMYC amplification or isochromosome 17q. ---- Comment: The presence of focal nodularity was accompanied by reduced proliferation and loss of reticulin content in some foci. It appears that we are seeing a predominant nodular pattern. This result, combined with the failure to detect the above cytogenetic alterations or Wnt pathway activation, suggests that this tumor may be driven by activation of the sonic hedgehog signaling pathway.
