Figure 2.

(a and b) Hematoxylin and Eosin staining of the tumor under low- and high-power microscopic fields revealing a highly cellular neoplasm composed of diffuse sheets of tumor cells having monomorphic, round to oval, finely vesicular nuclei and occasional nucleoli with indistinct cytoplasmic border. In some foci, tumor cells are grouped around small vessels (pseudo-rosette appearance). Several groups of mitotic figures were noted, but no necrosis was detected. (c) Immunohistochemistry study for CD99 depicting tumor cells highly positive for the marker