Fig. 2.

A, Histological sections show a highly cellular tumor composed of primitive cells with scant cytoplasm (hematoxylin and eosin; 200× magnification, scale 50 µm). Numerous mitotic figures are identified in even this small field. B, There is loss of SWItch/Sucrose Non-Fermentable–related, matrix-associated, actin-dependent regulator of chromatin, subfamily b, member 1 (SMARCB1) nuclear expression in the tumor cells (200× magnification, scale 50 µm). In comparison, SMARCB1 expression is retained in normal endothelial cells, which serve as internal controls. C, These tumors may have variable populations of rhabdoid cells, characterized by relatively abundant, eosinophilic cytoplasm and eccentrically placed nuclei (arrowheads; hematoxylin and eosin; 400× magnification, scale 20 µm).