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Washington University Experience | NEOPLASMS (MENINGIOMA) | Anaplastic | 17H Case 17 FISH & Denouement
17H FISH Studies and Denouement ---- FISH showed deletions involving 22q, 1p, and 14q in the areas of better differentiated meningothelial issue. Chromosome 9 polysomy, but no evidence of p16 region deletion was found. In sarcomatoid regions, there were similar deletions, although present in a small subset of cells. In addition, there was evidence of homozygous and hemizygous p16 deletions within a small subset of cells. ---- Case 17 Comment (FISH images no longer available): The morphologic, immunohistochemical, and genetic features support the interpretation of anaplastic meningioma with a rhabdomyosarcomatous component, WHO grade III. In the 2007 specimen, there is a better differentiated region consistent with atypical meningothelial and microcystic meningioma. Presumably, this was the precursor lesion. Genetic studies further show typical deletions found in high grade meningiomas. In sarcomatoid regions, a smaller fraction of the tumor cells show these alterations. This is difficult to explain with certainty. One possibility is a collision tumor with a second tumor type, namely a sarcoma. However, it is also possible that the faction of cells with deletions are underestimated due to increased polysomy in the sarcoma or that there are increased non-neoplastic elements in the sarcoma-like component (e.g., fibroblasts). Additionally, there was evidence of focal p16 region deletion. Studies have shown that anaplastic meningiomas with p16 deletion have a particularly aggressive biology.
