Tumor-like amyloid formation (amyloidoma) in the brain.

An almost walnut-sized tumor was removed surgically from the left occipital lobe of a 46-year-old woman, who had suffered for 4 year from progressive visual loss with scotoma and finally from hemianopia, associated with attacks of headaches and recurrent episodes of depression each lasting for some weeks or months. Neuropathological examination, including polarization, thioflavine, fluorescence, immunofluorescence staining, and electron microscopy, revealed an amyloidoma, which consisted of broad appositionally grown amyloid deposits surrounded by some plasma cells, monocytic or foreign body cell types. The massive accumulations, often associated not only with blood vessels or perivascular collagenous fibers but also lying in the cerebral tissue not unlike senile plaques in the cortical gray matter corresponded to gradually growing masses as seen in the repeated CT scans. This unique lesion in the brain of a patient who did not show any evidence of systemic disorder, seems to confirm that the spontaneous tumor-like amyloid, which gave an immunofluorescent staining mainly with anti-IgM, is a special variant of primary amyloidosis (amyloid L) or of so-called paramyloid.