[Primary intracerebral malignant fibrous histiocytoma: case report].

We report a rare case of a primary intracerebral malignant fibrous histiocytoma (MFH) with malignant progression from a premalignant stage. A 73-year-old male presented with mild hemiparesis on the right side of his body 4 months prior to admission. MR images showed a homogenously enhanced mass in the left parietal lobe. The patient underwent an uneventful extirpation of the solid mass. Microscopically, the solid tumor contained histiocytic cells and spindle-shaped fibroblastic cells arranged in a storiform pattern. The tumor cells were immunoreactive for vimentin, MAC 387 (macrophage marker) and alpha-1-antitrypsin. The MIB-1-positive rate was 1%. The histological diagnosis was fibrous histiocytoma. Postoperative MR images demonstrated no abnormally enhanced lesions. The patient's neurological symptoms and signs gradually improved. One year after surgery, he developed right hemiparesis. MR images showed a heterogeneously enhanced mass in the left sensorimotor area. This recurrent tumor was totally resected. Microscopically, the tumor was composed of atypical spindle-shaped cells, forming a storiform pattern. Pleomorphism was prominent, and necrotic foci were also seen. The MIB-1 labeling index averaged 11%. The histological findings corresponded to those of MFH. Unfortunately, the patient died of interstitial pneumonia contracted during postoperative radiotherapy. Early detection and resection at a stage of low malignant potential, followed by radiochemotherapy, are crucial for the management of this mesenchymal tumor.