Presentation
Not available.
Patient Data
There is a solid hyperdense mass in the midline of the posterior fossa. It seems intimately related in the inferior vermis, abutting in the floor of the fourth ventricle and extending through the foramen magnum.
The mass has homogenous enhancement with no diffusion restriction. There are prominent flow voids within the tumor. I note that the tumor is hyperdense on a non-contrast CT.
Mild hydrocephalus.
The remainder of the brain is unremarkable.
There is a lobulated mass in the midline of the posterior fossa measuring 24 x 32 x 30 mm (trans, AP, CC). It is intimately related in the inferior vermis and extends into the left cerebellar hemisphere. It abuts the floor of the fourth ventricle and partially effaces it and it extends through the foramen magnum and displaces the medulla anteriorly.
The mass has homogenous enhancement with no diffusion restriction. There are prominent flow voids within the tumor. I note that the tumor is hyperdense on a non-contrast CT.
Right frontal approach ventricular drain with tip in the right lateral ventricle. Mild hydrocephalus persists. The cisternal magna is enlarged.The remainder of the brain is unremarkable with no evidence of CSF seeding.
IMPRESSION: Vascular appearing posterior fossa mass centered in the inferior cerebellar with MRI appearances not pathognomonic of any one particular entity. The differential diagnosis is between choroid plexus papilloma, hemangioblastoma, ependymoma and pilocytic astrocytoma. Medulloblastoma is unlikely due to facilitated diffusion.
MICROSCOPIC DESCRIPTION: The sections show a moderately cellular papillary tumor. It has well-developed papillae with central fibrovascular cores. The lining cells have mildly enlarged and slightly clefted nuclei, generally small nucleoli and moderate amounts of clear foamy to pale eosinophilic cytoplasm. True ependymal rosettes or perivascular pseudorosettes are absent. Mitoses are inconspicuous. There are increased numbers of blood vessels at the tumor periphery but no microvascular proliferation is seen. No necrosis is identified. The tumor cells are diffusely CAM5.2 and focally GFAP positive. The topoisomerase index is 2%. They are transthyretin, synaptophysin, inhibin, EMA, CD10, Napsin-A, thyroglobulin and TTF-1 negative. The features are those of choroid plexus papilloma.
DIAGNOSIS: Posterior fossa tumor: Choroid plexus papilloma (WHO Grade I).
Case Discussion
Choroid plexus papilloma is an uncommon, benign neuroepithelial intraventricular tumor which can occur in both the pediatric (commoner) and adult population.