CD44 expression in human meningiomas: An immunocytochemical, immunohistochemical and flow cytometric analysis.

CD44 is a polymorphic family of cell adhesion molecules that has been implicated in tumour invasion and metastasis. In this comparative analysis study, we investigated the expression of the standard form of CD44 (CD44s or CD44H) in 25 early passage cultures of meningiomas and histological sections, using immunohistochemical, immunocytochemical and flow cytometry techniques. There were 20 grade I, 3 grade II and 2 grade III meningiomas in the study which also included 2 recurrent meningiomas and 1 meningioma arising some time after previous radiotherapy. Immunocytochemistry and flow cytometry results on early passage culture cells show that although the majority of the meningiomas were strongly positive for CD44H, some were only weakly positive. Immunohistochemical studies revealed a great variability in staining patterns both within individual tumours and between different tumours. Generally, the intensity varied between strong and negative, and in most tumours that were immunopositive, there was a multifocal pattern of staining. Five meningiomas did not stain at all for CD44H. Taken together, these findings suggest that generally the flow cytometry results correspond well with those of both immunocytochemical and immunohistochemical techniques, with a few exceptions. It is concluded that microenvironmental factors may be responsible for the differential expression seen with different techniques.