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.