Fig. 2

Case 1 A The tumor is comprised of a fairly bland population of neoplastic cells (H&E, 400X) B. Occasional multinucleated forms are present (H&E, 600 X). C. Many tumor cells express GFAP (GFAP, 600X) D. The vast majority of tumor cells are positive for OLIG2 (OLIG2, 200X). E. Scattered tumor cells are also positive for chromogranin (chromogranin, 400X). F. The Ki-67 labeling index was low (Ki-67, 200X). Case 2 A The tumor shows a mixture of bland mononuclear cells, and multinucleated cells with frequent microcalcifications. (H&E, 200X). B. A population of ganglioid cells is also present (H&E, 600X). C. A proportion of the tumor cells are positive for GFAP (GFAP, 400X). D. The tumors cell nuclei are diffusely positive for OLIG2 (OLIG2, 200X). E. NeuN is expressed in numerous cells within the tumor indicating neuronal differentiation (NeuN, 200X). F. The Ki-67 labeling index is low (Ki-67, 100X)