Birthmarks can occur on the conjunctiva as on the skin. They are usually located near the limbus in the temporal portion of the palpebral fissure, less frequently on the lacrimal caruncle. These benign, slightly raised epithelial or subepithelial tumors are congenital. Fifty percent of nevi contain hollow cystic spaces (pseudocysts) consisting of conjunctival epithelium and goblet cells. Conjunctival nevi may be pigmented (Fig.4.24a) or unpigmented (Fig. 4.24b), and they may increase in size as the patient grows older. Increasing pigmentation of the nevus as a result of hormonal changes during pregnancy or puberty or from exposure to sunlight can simulate an increase in the size of the nevus, as can proliferation of the pseudocysts. Conjunctival nevi can degenerate into conjunctival melanomas (50% of conjunctival melanomas develop from a nevus). Therefore, complete excision and histologic diagnostic studies are indicated if the nevus significantly increases in size or shows signs of inflammation.
H Photographs should always be taken during follow-up examinations of conjunctival nevi. Small clear watery inclusion cysts are always a sign of a conjunctival nevus.
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