Extremely rare case of isolated cerebellar amyloidoma: a short report.

Brain amyloidoma is an exceedingly rare localized deposition of amyloid that often radiologically mimics neoplastic or inflammatory disease. We report the case of a previously healthy 53-year-old woman who developed subacute right-hand tremor, pain, and weakness, followed by gait instability. Magnetic resonance imaging (MRI) showed a 35-45 mm hypervascular, infiltrative lesion in the right cerebellar hemisphere, extending into the vermis and middle cerebellar peduncle, with ill-defined margins suggesting of posterior fossa tumor. Subtotal resection was performed. Histopathology confirmed amorphous Congo-red positive amyloid material with perivascular and parenchymal distribution, accompanied by lymphoplasmacytic infiltrates lacking light-chain restriction and therefore without evidence of monoclonality, consistent with amyloidoma. According to the literature, fewer than 100 cases of intra-axial brain amyloidoma have been reported, with infratentorial presentations being extremely uncommon and none previously have been described as an isolated intra-axial cerebellar lesion. This case expands the recognized anatomical spectrum of cerebral amyloidoma, highlights its diagnostic pitfalls, and underscores the essential role of histopathology in establishing the diagnosis.