Imaging characteristics are most consistent with an ependymoma, although the location of the tumor is less typical in this age group. A choroid plexus papilloma is felt less likely given the not so vivid enhancement. 


MICROSCOPIC DESCRIPTION: 1-2. Sections show a moderately cellular tumor with a fibrillary background forming prominent perivascular pseudorosettes and focal ependymal canals. No true ependymal rosettes are seen. Tumor cells demonstrate mildly enlarged elongated nuclei and small nucleoli. No mitoses, necrosis or microvascular proliferation are seen. Immunohistochemically tumor cells stain:

  • GFAP+
  • ATRX+
  • IDH1-
  • p53-
  • EMA-.
  • Ki67 proliferation index is approximately 5%.

DIAGNOSIS: 1-2. Brain, 4th ventricle lesion: Ependymoma (WHO Grade II)

Slide images courtesy of the RMH Pathology Department.