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Washington University Experience | NEOPLASMS (MENINGIOMA) | Meningioma - Clear cell | 24B Case 24 Denouement
Ancillary information & Denouement Stains for CD34 from both specimens highlight endothelial cells, though the tumor cells are negative. The tumor cells are strongly positive for vimentin and this highlights variable spindled and epithelioid cellular morphologies. The majority of tumor cells are negative for epithelial membrane antigen (EMA), though there are individual bands of tissue throughout the tumor that show variable degrees of immunoreactivity. A repeat EMA immunostain similarly shows weak to moderate immunoreactivity within band-like collections of spindled cells within the tumor. The tumor cells are negative for cytokeratin, GFAP, and synaptophysin. The histochemical stain for trichrome highlights dense collagen deposition throughout the tumor. Additionally, histochemical stains for PAS with and without diastase highlight glycogen deposition in many of the more epithelioid-appearing cells. The Ki-67 labeling index in both specimens was estimated at approximately 5%. A stain for smooth muscle actin shows strong immunoreactivity within a subset of the spindled cells. However, the cells are completely negative for desmin. Therefore, this population of cells likely represents myofibroblasts within the desmoplastic stroma. Rare cells are positive for S-100 protein. There is no synaptophysin immunoreactivity in tumor cells. The tumor cells are strongly and diffusely immunoreactive for BCL2 and there is patchy membrane-pattern immunoreactivity for CD99 (013). ---- FISH studies were performed to help resolve the differential diagnosis of meningioma vs. hemangiopericytoma vs. Ewing sarcoma/PNET. FISH was performed utilizing probes against NF2, BCR, CEP18, DAL1 (protein 4.1B), 1p32, and 14q32. Additionally, a EWS breakapart probe was utilized. These studies showed deletions involving NF2, BCR, and the telomeric portion of the EWS probe set. There were normal dosages (2 copies) of CEP18, DAL1, 1p32, 14q32, and the centromeric portion of the EWS probe set. This pattern is consistent with a complex chromosome 22q rearrangement that includes deletions of multiple regions, including the NF2 gene itself. Although not entirely specific, this genetic pattern supports the diagnosis of meningioma. ---- The morphologic, immunohistochemical, and genetic data are consistent with the diagnosis of atypical meningioma with clear cell features, WHO grade II in both the 2003 and 2005 specimens. This is an old case; a STAT6 immunostain perhaps with a SSTR2A to define a SFT or meningioma marker might quickly resolve this question.
