Choroid plexus metastasis - from renal cell carcinoma
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There is a 23 x 29 x 28 mm lobulated lesion centred either within the left superomedial temporal lobe. Its epicentre is difficult to clearly localise. It may be in the parenchyma of the temporal lobe extending into the posterior external capsule and posterior to the left lentiform nucleus or in the choroid plexus with extraventricular extension. It is partially solid / cystic with vivid enhancement of internal septae. This has local mass effect, with extensive surrounding vasogenic oedema, sulcal effacement, partial effacement of the left ambient cistern and lateral ventricle. The temporal horn of the left lateral ventricle, which is entrapped / dilated. This is a solitary lesion.
Elsewhere non specific deep white matter foci are seen most likely related to small vessel ischaemia.
1 case question available
This patient had a prior history of renal cell carcinoma and nephrectomy 2 years previously without evidence of metastatic disease. He went on to have a craniotomy and resection of the mass, at which time it was still difficult to identify the site of origin as both the choroid plexus and adjacent brain were involved.
MICROSCOPIC DESCRIPTION: Sections show a moderately cellular tumour surrounded by pools of blood and only a small amount of brain parenchyma. The tumour comprises clusters of cells intersected by a rich vascular network. The tumour cells have ovoid mildly pleomorphic nuclei, inconspicuous nucleoli and moderate amount of granular to clear eosinophilic cytoplasm. Some cells show well defined cytoplasmic outlines. Mitotic activity is inconspicuous.
The tumour cells are CD10 and Vimentin positive but Inhibin, S-100, CK7, CK20, TTF-1, CDX-2 negative. The morphological and immunohistochemical features are of a metastatic renal cell carcinoma.
FINAL DIAGNOSIS: Metastatic renal cell carcinoma.
2 case question available
Renal cell carcinoma is one of the classic primary carcinomas to metastasis to choroid plexus, often as an isolated lesion.