The sections show fragments of a moderately hypercellular ependymoma. Tumour cells have mildly pleomorphic vesicular nuclei with a finely granular chromatin. Well formed perivascular pseudorosettes are noted throughout all fragments submitted. Annotated Figure 1: A) tumour cells B) 'clear area' and C) central vessel.
A very occasional mitotic figure is identified (1/20 HPF). There is no microvascular proliferation. Two small areas of bland infarct-like necrosis are noted.
Immunohistochemistry shows prominent perinuclear dot staining for epithelial membrane antigen (EMA) in tumour cells as well as strong staining for GFAP. The topoisomerase labelling index is approximately 10%.
DIAGNOSIS: Posterior fossa ependymoma (WHO Grade 2).
Note: as molecular profiling is unavailable in this case, it would have the diagnosis of posterior fossa ependymoma not otherwise specified (NOS).