CD68 and Factor XIIIa expressions in granular-cell tumor of the skin

Immunohistochemical and electron microscopic studies support a Schwann cell origin for most of the granular-cell tumors of the skin. We studied 9 granular-cell tumors by immunohistochemistry, using antibodies to CD68, S-100 proteins, factor XIIIa, L1 antigen, desmin and vimentin. The CD68 monocyte-macrophage-associated lysosomal antigen was expressed in granular cells which however had no Mac 387 reactivity. The 'satellite fibroblasts' were factor XIIIa-positive similarly to dendrocytes and perineurial cells. Our study reveals the lack of specificity of CD68 antibody to identify macrophages. It also presents granular cell tumor of the skin as an exception in the group of schwannomas by the presence of factor XIIIa-positive cells inside the neoplasm.