Fig. 5

Histologic examination of the specimen revealed a hypercellular tumour composed of spindle-shaped cells in fibromyxoid matrix, with a hemangiopericytoma-like pattern (a). Tumour cells had clear to eosinophilic cytoplasm, nuclei were oval or elongated, of monomorphic appearance, with no signs of atypia. Mitotic figures were rarely seen. Surrounding bone trabeculae were irregular in size and shape with wide osteoid seams and foci of hyaline cartilage, showing enchondral ossification (b, c). The tumour cells were strongly and diffusely positive with vimentin (d) but exhibited no reactivity with PanCK, SMA, CD34, CD10 and D2-40 (year 2014)