A case of pterygium-like proliferation containing postoperat
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Pterygium is a triangular fibrovascular proliferation that usually extends from the nasal conjunctiva and encroaches upon the cornea. Histopathologically, primary pterygium is characterized by epithelial proliferation, epithelial-mesenchymal transition, and an activated fibroblastic stroma with inflammation, neovascularization, and matrix remodeling.

A 79-year-old woman complained of blurred vision in her left eye presumably due to pterygium-like tissue growth. She had a medical history of limbal dermoid from birth, which was removed at 12 years of age. Her decimal best-corrected visual acuity (BCVA) was 1.2 oculus dexter and 0.5 oculus sinister (OS) with hyperopia. Slit-lamp microscopy revealed a markedly thick growth of pterygium-like triangular ocular surface tissue from the temporal conjunctiva toward the apex of the cornea. Corneal opacity was observed around the head of the tissue oculus sinister. Because of visual impairment with severe irregular astigmatism, we performed pterygium surgery and ocular surface reconstruction. Eight months after the operation, her best-corrected visual acuity improved to 0.8 oculus sinister without an obvious recurrence of the lesion.

Histopathological findings
The head of the excised tissue was histologically covered with stratified columnar epithelium mixed with goblet cells and squamous metaplasia. Dense collagenous tissue was located beneath the epithelium, where a collection of degenerated elastic fibers was intermingled. Unexpectedly, the body of the excised tissue contained a peripheral nerve in the subepithelial stroma surrounded by a number of dilated neovessels and collagen fibers. The body of the excised tissue also contained mature adipose cells and collagen fibers.

Immunohistochemistry for Ki67, a cell proliferation marker, was further confirmed. Briefly, the slide was dewaxed, rehydrated, and rinsed in phosphate-buffered saline twice for 10 min. As a pretreatment, microwave-based antigen retrieval was performed in 10 mM citrate buffer. The slide was treated with 3% hydrogen peroxide and normal goat serum. Sections were incubated with anti-Ki67 antibody. Positive signals were visualized using 3, 3 -diaminobendizine as a substrate. Hematoxylin staining was conducted for nuclear staining. Cells were examined using a Biorevo BZ-9000 microscope. Ki67 was immunopositive in the nuclei of pterygial epithelial cells and neovascular endothelial cells but not in the connective tissue, the adipose tissue, or the peripheral nerve.

In conclusion, the development of the present case would thus be attributable to the etiology common to primary pterygium but modified to some extent by non-proliferative residual dermoid tissue.