A nevus near the limbus is usually almost flat. Nevi appearing elsewhere on the bulbar conjunctiva, plica semilunaris, caruncle, or eyelid margin tend to be elevated. Pigmentation of conjunctival nevi is variable: they may be light tan to brown or amelanotic (15% of cases; Fig 12-9). A subepithelial nevus often has a cobblestone appearance.
Small epithelial inclusion cysts occur within approximately half of all conjunctival nevi, particularly the compound or subepithelial varieties. Secretion of mucin by goblet cells in the inclusion cysts can cause a nevus to enlarge, giving a false impression of malignant change. Cellular proliferation may induce secondary lymphocytic inflammation. Rapid enlargement can occur at puberty, giving rise to a clinical impression of conjunctival melanoma. An amelanotic, vascularized nevus, when inflamed, may resemble an angioma, or it may be misdiagnosed as chronic conjunctivitis. See Table 12-3 for a clinical comparison of the various pigmented lesions of the conjunctiva.
Figure 12-9 Amelanotic conjunctival nevus.
(Courtesy of Kathryn Colby, MD, PhD.)
Jakobiec FA, Sandhu H, Bhat P, Colby K. Bilateral conjunctival melanocytic nevi of simultaneous onset simulating conjunctivitis in a child. Cornea. 2010;29(8):937–940.
Shields CL, Fasiuddin AF, Mashayekhi A, Shields JA. Conjunctival nevi: clinical features and natural course in 410 consecutive patients. Arch Ophthalmol. 2004;122(2):167–175.
Conjunctival nevi rarely become malignant and can be followed with an examination every 6–12 months that includes serial photography or detailed slit-lamp drawings incorporating dimensional measurements. Excisional biopsy should be performed on lesions that show suspicious change or growth. A biopsy should also be performed for pigmented lesions on the palpebral conjunctiva or cornea or in the fornix, as nevi are rare in these locations.