Clinicopathological features of solitary fibrous tumor of the meninges: Animmunohistochemical reappraisal of cases previously diagnosed to be fibrous meningioma or hemangiopericytoma

Cases of solitary fibrous tumor (SFT) of the meninges are increasingly bein g reported. However, the real incidence of SFT among meningeal tumors has y et to be determined. We therefore clinicopathologically re-examined 64 meni ngeal tumors originally diagnosed to be either fibrous meningioma (FM group , n = 46) or hemangiopericytoma (HPC group, n = 18) while paying special at tention to SFT. We thus reclassified one case from the FM group (2%) and on e case from the HPC group (6%) to be SFT, both of which showed diffuse CD34 -immunoreactivity and dense intercellular reticulin fibers but neither epit helial membrane antigen nor S-100 protein expression. The MIB-1 staining in dex of these cases were 6.2% and 3.9%, respectively. The former recurred 15 years after the initial surgery and the patient underwent a second removal of the tumor. The patient has been alive with no evidence of recurrence fo r 7 years after the second surgery. The latter patient has been alive with no evidence of recurrence for 3 years postoperatively. The results confirme d that the incidence of SFT among meningeal tumors is relatively low, howev er, because of its clinically indolent nature, a careful histochemical exam ination is necessary to differentiate SFT from other neoplasms with a more aggressive nature. Our findings emphasize the need to clinically recognize this lesion as a distinct entity.