Acute deterioration in level of consciousness. Scanned on arrival in the emergency department.
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A large rounded mass is present in the posterior fossa, centered on the fourth ventricle. Centrally it is of high attenuation, consistent with hemorrhage. Following administration of contrast, moderate enhancement of the solid component is seen.
There is marked obstructive hydrocephalus and a little blood is also seen pooling in the occipital horns.
In a 30 year old the differential for a posterior fossa hemorrhagic mass is mainly between a hemangioblastoma and an ependymoma, although hemorrhage in both is quite uncommon. Pilocytic astrocytomas can rarely hemorrhage as can medulloblastomas, however in both cases the age group is a little atypical. Metastases would be unusual in a patient of this age.
The sections show multiple fragments of variably but up to moderately cellular tumor. Part of the tumor has an ependymal lining but the tumor has a distinctive pattern of moderately pleomorphic oval nuclei with speckled chromatin in a neurofibrillary background. Perivascular pseudorosetting is a prominent feature. In areas, true rosettes with lumens are also noted. Areas of tumor necrosis are not seen but there are focal collections of hemosiderin-laden macrophages and focal fibrosis is noted. An occasional mitotic figure is noted. The features are those of a classical ependymoma.
DIAGNOSIS : Posterior fossa tumor - ependymoma, WHO grade 2.