Posterior fossa ependymoma
This patient went on to have a posterior fossa craniotomy and resection of the tumor.
Sections show an ependymal tumor showing perivascular pseudorosette formation. Localized foci of recent tumor necrosis are identified. Vascular proliferation is not seen. Increased mitotic activity is not observed.
FINAL DIAGNOSIS: Ependymoma containing foci of recent tumor necrosis.
Note: as molecular profiling was not carried out in this case, it would have the diagnosis of posterior fossa ependymoma not otherwise specified (NOS).
This case demonstrates fairly typical imaging features of a posterior fossa ependymoma. Tumor necrosis, which was focally noted in this ependymoma, is one histologic parameter used for grading ependymomas. There were no other histologic features associated with aggressive biologic behavior in this sample. It should be noted that the correlation between tumor necrosis and biologic behavior is not as stringent in ependymomas as in diffusely infiltrating astrocytomas.