Cytology and immunohistochemistry of anaplastic meningiomas in squash preparations. A report of two cases.

Cytodiagnosis is a useful adjunct to frozen section diagnosis of brain tumors during surgery and has been applied in many pathology laboratories. Although anaplastic (malignant) meningiomas are not extremely rare tumors, their cytologic features have not been well described. Cytologic details of anaplastic meningioma, papillary meningioma with a fibroblastic component and anaplastic angiomatous meningioma are presented. Papillary meningioma showed atypical cell clusters having a close relation to mature endothelial cells and that corresponded to papillary proliferation. Other cell clusters of this tumor showed an ordinary fibroblastic pattern with coarse cytoplasmic filaments and necrotic changes in the cytoplasm. Anaplastic angiomatous meningioma exhibited loose cell clusters. Some of them had coarse cytoplasmic filaments, and others were similar to epithelial cells in origin. Specific features commonly found in anaplastic meningioma were hyperchromatic and pleomorphic nuclei and cytoplasmic filaments more obscure than those of the benign counterpart. Immunocytochemically the tumor cells in the papillary area of papillary meningioma had a positive reaction to antiserum of vimentin, cytokeratin and S-100 protein. The tumor cells of anaplastic plastic angiomatous meningioma showed intracytoplasmic positivity to antivimentin and anti-epithelial membrane antigen serum.