Expression of beta 2 integrins and macrophage-associated antigens in meningeal tumours

This study assessed the expression of leukocyte integrins and macrophage-as sociated antigens in meningiomas. Fourteen benign meningiomas, ten atypical /anaplastic meningiomas, two hemangiopericytomas and one solitary fibrous t umour (SFT) were included. Frozen sections were immunostained using antibod ies directed against leukocyte integrins, CD68, CD14, CD2, CD1a, DRC1 and C D34. Their expression was evaluated semi-quantitatively. Ki67 positive cell s were counted. Arachnoid membranes served as controls. Arachnoid cells exp ressed the beta 2-integrin subunit and KP1. Beta2 was detected in the tumou r cells of 14 meningiomas. In nine cases, this was associated with an alpha -integrin subunit. There was no statistical difference in the expression of beta 2 between benign and atypical/anaplastic meningiomas. KP1 was constan tly expressed by the tumour cells of meningiomas. It was not expressed by o ther meningeal rumours. CD34 was detected in the fibrous meningiomas, heman giopericytomas and the SFT. In each tumour, macrophages were more numerous than T lymphocytes. There was no statistical difference in the density of m acrophages and T lymphocytes between the benign and atypical/anaplastic men ingiomas. There was no correlation between the Ki67 proliferation index and macrophage infiltration. Meningiomas, through the expression of leukocyte antigens, have a very particular phenotype. The expression of beta 2 integr ins could play a role in the attraction of immunocompetent cells in the str oma of meningiomas.