Fig. 2

a: Macroscopic photograph of the intraventricular tumor. The main part of the tumor was encapsulated and solid (white arrow). The bottom part of the tumor became prominent and soft (black arrow). b-i: Histopathology of the main part shown with a white arrow in Fig. 2a. This region consisted of spindle-shaped fibrous cells, including a large amount of collagen deposits (b, hematoxylin & eosin (HE) stain). Using immunochemistry, the cells positively stained for vimentin (c), epithelial membrane antigen (EMA) (d) and S-100 protein (e), but were negative for cytokeratin (f), Schwann 2/E (g), GFAP (h), Olig2 (i) and lymphocytic markers (data not shown). These cellular profiles confirmed the histological diagnosis of the tumor as fibrous meningioma (WHO grade I). j-r: Histopathology of the part shown with a black arrow in Fig. 2a. This region showed increased cellularity, and cells were large, atypically shaped with multiple nuclei and prominent nucleoli (j). Mitotic cells were confirmed by examining more than 20 percent high-power fields on HE (j) and Ki67 stain (k). The cells with a malignant appearance were also positive for vimentin (l), EMA (m), S-100 protein (n) and cytokeratin (o), but negative for Schwann 2/E (p), GFAP (q) and Olig2 (r); This part of the tumor was diagnosed as anaplastic meningioma (WHO grade III)