Subependymoma with extensive microcystic transformation: a case report.

Subependymomas are benign tumors that occur predominantly in the ventricular system. We described a case of a 44-year-old female with a large subtentorial mass which compressed the brain stem and fourth ventricle. Complete surgical excision of the tumor was achieved. The tumor composed of collections of cytologically bland cells with round to oval nuclei set within wide expanses of a delicate fibrillar matrix, and extensive microcystic changes were found. The tumor demonstrated positive staining with GFAP and S-100 protein, and did not stain with antibodies to Neu-N or Progesterone receptor, patchy expression of Epithelial Membrane Antigen. An MIB-1 labeling was lower than 1%. The tumor was totally resected and didn't recur after the initial surgery.