Contributions of immunohistochemistry and electron microscopy for the diagnosis of meningeal hemangiopericytomas

Meningeal hemangiopericytomas (NPC) are rare CNS tumors with a pour prognos is compared to meningiomas. In order to define diagnosis criteria, we perfo rmed an immunohistochemical and ultrastructural study in respectively 15 an d 5 meningeal HPC. The following antibodies anti-KL1, EMA, vimentin, CD34, factor VIII, alpha -smooth actin, estrogen and progesteron receptors (RE, R P) were used in paraffin embedded sections whereas anti-NCAM and E-cadherin antibiodies were used on frozen sections when available. We can differenti ate meningeal HPC from meningioma because of a complete lack of immunostain ing with epithelial markers as well as with NCAM antibody or RE and RP rece ptors. Besides a positivity with CD34 and alpha -smooth actin antibodies wa s always observed even focally in HPC. On the other hand solitary fibrous t umor showed a strong and diffuse positivity with anti CD34 and antivimentin antibodies. Electron microscopy can be helpful in some instances showing m embrane basal-like substance and absence of desmosomes.