CD34 IMMUNOREACTIVITY IN NERVOUS-SYSTEM TUMORS

CD34 is a sialylated transmembrane glycoprotein of unknown function th at is present in myeloid progenitor cells, endothelial cells, and some fibroblast-related mesenchymal cells. However, its tissue distributio n is still incompletely characterized. In this study we evaluated the distribution of CD34 antigen in tumors of the central and peripheral n ervous system. For comparison the tumors were also stained for CD31, a lso known as platelet-endothelium cell adhesion molecule (PECAM-1), a transmembrane glycoprotein so far considered to be endothelium specifi c beyond its reactivity with certain hematopoietic cells. Neurofibroma s showed consistently high numbers of CD34-positive spindle cells, whe reas peripheral and acoustic schwannomas were negative. A subset of me ningiomas (15%) showed CD34-positive tumor cells, and some were also w eakly positive for CD31. Gliomas were negative. Meningeal hemangioperi cytomas were consistently CD34 positive, but CD31 negative. These resu lts indicate a moderately widespread distribution of the CD34 antigen in nervous system tumors, and necessitate caution in making conclusion s regarding endothelial cell differentiation of nervous system tumors on the basis of CD34 immunoreactivity.