[Pterygium and mast cells--mast cell number, phenotype, and localization of stem cell factor]

We examined the number and phenotype of mast cells, and the localization of stem cell factor (SCF) as a growth factor of mast cells in the excised tissue of 38 cases of pterygium. In histopathology with toluidine blue stain and immunohistochemistry with a monoclonal antibody to tryptase, the mean mast cell count in pterygium specimens was twice as high as in normal conjunctiva. In pterygium specimens more than 94% of tryptase-positive mast cells were found to express chymase and c-kit. There was no phenotypic difference between mast cells in pterygium and normal conjunctiva. In all immunohistochemical specimens in which we could examine the head of the pterygium, SCF was expressed in subepithelial fibroblasts at the central edge of pterygium. The results suggest that overexpression of SCF was accompanied with the augmentation of mast cells in the pterygium.