Idiopathic granulomatous meningoencephalitis presenting as an intracranial tumor.

A 2-year-old girl presented with a single episode of generalized seizure. Magnetic resonance imaging examination showed an intracranial mass with a diameter of 2.5 cm in the right parieto-occipital region of the cerebrum. These clinicoradiological findings were suggestive of intracranial tumor. Histologically, fibroblastic proliferation of storiform pattern was noted, associated with epithelioid granulomas. The etiological pathogens for the granulomas could not be detected even though investigation of special histochemical staining, immunohistochemical study and DNA analysis of Mycobacterium tuberculosis by polymerase chain reaction technique was performed. On electron microscopic examination, the area appearing as a storiform pattern consisted of fibroblasts showing much dilated rough endoplasmic reticulum and slender tappering cytoplasmic processes without cellular junctional complex. No organisms were identified in the granulomatous area of the lesion. From those findings the diagnosis as idiopathic granulomatous meningoencephalitis was made.