Giant cell reparative granuloma of the temporal bone: neuroradiological and immunohistochemical findings.

A 38-year-old man presented with a giant cell reparative granuloma (GCRG) of the left temporal bone. Computed tomography showed a osteolytic middle cranial mass lesion. Magnetic resonance (MR) imaging showed the lesion as low intensity with heterogeneous enhancement by gadolinium on the T1-weighted images, and extremely low intensity on the T2-weighted images. Angiography showed the lesion as highly vascular and fed by branches of the left external carotid artery. After preoperative embolization, gross total removal of the tumor was performed. The postoperative course was uneventful and no evidence of recurrence has been found for more than 4 years. Histological examination revealed GCRG with multinucleated giant cells in the fibrous background, abundant collagen bundles, hemosiderin deposits, and trabeculae of reactive bone. Some of the mononuclear stromal cells and almost all of the giant cells were positive for CD68, suggesting histiocytic differentiation. These histological features reflect the marked decrease in signal intensity on T2-weighted MR images.