Figure 3. Histopathological examination of the extradural tumor specimen of the 82-year-old man. (A, B) Low-power photomicrographs of the tumor sections (hematoxylin-eosin stain, original magnification ×5 [A], ×20 [B]) reveal a well-circumscribed mesenchymal tumor with osseous fibrous rim (arrows) and thick collagenous capsule (arrowheads). (C) High-power photomicrographs (hematoxylin-eosin stain, original magnification ×100 [C], ×200 [B]) reveal uniformly round-to-ovoid-shaped tumor cells arranged in nests of clusters (circles, B, C) within a myxoid and hyalinized stromal matrix (curve arrow, C) indicating its stromal origin. There is scattered nuclear atypia with mitotic activity in 2 per 50 high-power fields (arrows, D). Immunohistochemistry (not shown) of the tumor specimen reveals strong positivity for vimentin, and patchily positive for EMA, CD99 and AE 1/3. (E) There is a high Ki67 proliferation index of 40–50% (original magnification ×10). Overall microscopic examination reveals a malignant ossifying fibromyxoid tumor FNCLCC (Federation Nationale des Centres de Lutte Contre le Cancer) grade 2.