Granulomatous cerebral angiitis
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A large heterogeneous enhancing mass centered on the left basal ganglia is demonstrated which measures approximately 5 cm in diameter. It extends to involve the temporal lobe, insular cortex, posterior aspect of gyrus rectus, and extends across the midline via the anterior commissure into the right internal capsule. It is surrounded by a mantle of high T2 signal, and exert significant positive mass effect with 8 mm of midline shift. No hydrocephalus. Centrally within this lesion and areas of non-enhancement, with petechial regions of signal loss on EPI is probably representing blood product. No restricted diffusion.
A 2nd focus of high T2 signal with enhancement is seen in the right frontal lobe involving the inferior frontal gyrus. This area is not continuous with the 1st, with no bridging high T2 signal between the two regions.
A 3rd region also with high T2 signal and subtle enhancement involves the left side of the medulla and inferior cerebellar peduncle and floor of the 4th ventricle just lateral to the facial colliculus.
Multifocal intracranial enhancing masses has a differential of multifocal high-grade glioma or multifocal CNS lymphoma. Heterogeneous enhancement, and (to a lesser degree) absence of restricted diffusion favor the former whereas the distribution and character of enhancement is more suggestive of lymphoma.
Paraffin sections show fragments of white matter with scatterd mature neurones. There is an angiocentric pattern of accumulation of small lymphoid cells which are predominantly T cells (CD3+, CD4+, CD8+) with smaller numbers of CD20+ B lymphocytes. There are also prominent CD68+ monocyte-macrophages both adjacent to small calibre blood vessels and within the intervening parenchyma. Foci of incipient necrosis are also noted and there is prominent reactive astrocytic gliosis. An occasional poorly formed granuloma composed of CD68+ monocyte-macrophages and lymphocytes is present adjacent to a blood vessel. The majority of blood vessels show distortion of their structure with swollen reactive endothelial cells. Some vessels show fibrinoid necrosis. In situ hybridization and immunohistochemistry for EBV are negative.
DIAGNOSIS: Features favour granulomatous cerebral angiitis (reviewed by a number of neuropathologists)
This is a difficult case both on imaging and histology, but is felt most likely to represent granulomatous cerebral angiitis.