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Rebecca Weiss, Maria Abadi, Alexandra Herzlich, Takayuki Nagasaki, JOYCE MBEKEANI; Comparative Evaluation of Typical and Atypical Pterygia Using Stem Cell and Germ Cell Markers. Invest. Ophthalmol. Vis. Sci. 2019;60(9):6254.
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© ARVO (1962-2015); The Authors (2016-present)
Pterygia are common, benign ocular surface growths; however, studies have shown a small proportion of pterygia display atypical histologic features. In a previous study, we observed squamous dysplasia and choristomas in a minority of pterygium specimens. We sought to investigate the expression of stem cell and germ cell markers in these atypical pterygia compared to typical pterygium specimens in order to gain more insight into the pathophysiology of pterygia and possible association with premalignancy.
We performed a retrospective chart review to identify cases of atypical pterygium histopathology and compared them to age-matched typical pterygium histopathology from January 2000 to December 2015. All preserved specimens were stained with the stem cell markers p63 and CK19 as well as the germ cell marker OCT3/4. Staining patterns were analyzed by a single pathologist.
Seven atypical pterygium specimens were identified: two with squamous dysplasia and five with simple and complex choristomas. The choristomas were comprised of cartilaginous, adipose, glandular and nervous tissue. We found diffuse p63 staining of conjunctival basal and suprabasal epithelial cells, but only focal staining of corneal epithelium within typical pterygium specimens. Squamous atypia/dysplasia associated with pterygia demonstrated strong, diffuse, full thickness staining of the epithelium with p63. Mesenchymal (cartilage, adipose tissue) and glandular choristomas did not express p63. In both typical and atypical specimens, CK19 was expressed in the conjunctival epithelium but not within the advancing epithelial edge of the pterygium that grows onto the cornea. Choristomas of mesenchymal origin did not express CK19 while those of epithelial origin, such as glandular tissue, did express CK19 in the same pattern as the surface epithelium of typical pterygia. OCT3/4 was variably expressed in typical and atypical conjunctival epithelium and stroma and displayed marked staining within the epithelium and stroma of atypical pterygia associated with mesenchymal choristomas.
Strong p63 and CK19 immunoreactivity within pterygium specimens may suggest that pterygia arise from limbal stem cell progenitors. Strong OCT3/4 expression in atypical pterygia associated with mesenchymal choristomas suggests a primitive state of pluripotency and may therefore predispose to recurrence and potential for malignancy.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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