CD34 and dural fibroblasts: the relationship to solitary fibrous tumor andmeningioma

Intracranial solitary fibrous tumors (SFTs) are typically dural-based, CD34 -positive neoplasms of uncertain histogenesis. We examined ten cases of men inges obtained at autopsy from patients with no history of neurological ill ness, head trauma, or neurosurgical intervention, and ten cases of typical meningiomas with attached dural margins not involved by tumor. All cases we re immunostained with CD34. CD34 reactivity was noted in the long, thin del icate processes of dural fibroblasts preferentially located in the meningea l portion of the dura rather than the periosteal portion. No CD34 reactivit y was identified in the arachnoid or pia mater, except in some endothelial cells. One supratentorial dural-based fibrous nodule and one SFT within the confines of the fourth ventricle showed strong and diffuse reactivity to C D34, bcl-2, and vimentin, and were negative for epithelial membrane antigen (EMA), S-100 protein, glial fibrillary acidic protein, smooth muscle actin , and desmin. We also describe a meningothelial meningioma within which a w ell circumscribed SFT-like nodule was embedded. The SFT-like nodule was str ongly CD34 positive and EMA negative, and the meningioma was strongly EMA p ositive and CD34 negative. Fibroblasts of the dural border cell layer are a ttached to the underlying arachnoid, and their inclusion with arachnoidal s tromal elements and pial-based tela choroidea during formation of choroid p lexus interstitium may account for intraventricular SFTs. Our results sugge st that SFTs and dural-based fibrous nodules derive from CD34-positive dura l-based fibroblasts, and that CD34 reactivity in meningiomas may result fro m inclusion of dural fibroblasts within the neoplasm.