Distribution of Vimentin-Expressing Cells in Pterygium: An Immunocytochemical Study of Impression Cytology Specimens

Abstract

To investigate the distribution of vimentin-expressing cells in human pterygium by immunocytochemical analysis of impression cytology specimens. Using impression cytology, 3 samples of superficial conjunctival epithelial cells, including pterygium and adjacent conjunctiva were obtained from each of 24 eyes of 24 patients with unilateral primary pterygium, 16 eyes of 16 patients with unilateral recurrent pterygium, and the 40 unaffected fellow eyes. Specimens were processed in avidin-biotin complex immunostaining system with monoclonal anti-vimentin antibody and/or anti-CD1a antibody and counterstained with hematoxylin. Under light microscopy, the extent of vimentin-expressing cell infiltration beyond the pterygium margin was measured with a micrometer and the number of vimentin-expressing cells was counted in each of 6 randomly selected high-power fields in the specimens of pterygium and normal conjunctiva. Two types of cells expressed vimentin, epithelioid cells and dendritic cells, whereas cells that expressed CD1a showed only a dendritic pattern. Vimentin-expressing round epithelioid cells (presumed pterygial cells) were present over the entire surface of the pterygium and also on adjacent normal-appearing conjunctiva, up to an average of 3.01 +/- 0.83 mm beyond the superior margin and 3.14 +/- 0.99 mm beyond the inferior margin of primary pterygium and 3.72 +/- 0.85 mm and 3.58 +/- 0.98 mm beyond the superior and inferior margins of recurrent pterygium. For the superior margin but not the inferior margin, the clinically occult extension of vimentin-expressing epithelioid cells was statistically significantly greater for eyes with recurrent pterygium compared with those with primary pterygium (P = 0.016). The density of dendritic (Langerhans) cells, stained by anti-vimentin and anti-CD1a antibodies, was statistically significantly lower in normal fellow eyes than in eyes with either primary (P < 0.001) or recurrent (P = 0.024) pterygium. The vimentin-expressing epithelioid cells were present not only over the ocular surface of the pterygium but also in the normal-appearing conjunctiva adjacent to primary and recurrent pterygium. The increased density of Langerhans cells in pterygium might reflect a higher level of antigenic and mitogenic exposure in the conjunctiva. However, the significance of these 2 phenomena in the recurrence and pathogenesis of pterygium remains undetermined and merits further studies.