Isolated angiitis in the hypothalamus mimicking brain tumor.

A 64-year-old female presented with exaggerating somnolence without contributory medical and lifestyle histories. She was not aware of any preceding infection or headache. Cerebral magnetic resonance imaging demonstrated an isolated enhanced mass in the hypothalamus without meningeal enhancement. Blood and cerebrospinal fluid examinations showed no significant findings except for hypernatremia and hyperprolactinemia. She underwent an open biopsy via the interhemispheric route. Histological examination revealed marked perivascular lymphocytic aggregation with polyclonal immunostaining both for B and T lymphocytes. No findings suggestive of underlying malignancy were recognized. Extensive work-up aiming at systemic vasculitis and lymphoma revealed no signs of extracranial lesion, so the most probable diagnosis was isolated angiitis in the hypothalamus. Angiitis may originate from the hypothalamus and should be considered in the differential diagnosis of hypothalamic lesion mimicking brain tumor on neuroimaging.