We report a case of giant conjunctival nevus and compare differential diagnosis between giant conjunctival nevus and conjunctival malignant melanoma.

A 46-year-old male presented with brown and elevated conjunctival mass in his right eye since childhood. The mass was located at the superior bulbar conjunctiva involving the superior cornea. The mass was 16 × 9 mm in size and elevated. Feeding vessels, intrinsic vessels and various cyst sizes were observed inside the mass. Resection of the conjunctival mass and amniotic membrane transplantation were performed. The histopathological diagnosis was conjunctival nevus.

Conjunctival nevus is a benign conjunctival tumor with excellent prognosis, often confused with conjunctival melanoma. Both conjunctival nevus and conjunctival malignant melanoma are commonly located in the bulbar conjunctiva, pigmented and often have feeder and intrinsic vessels. Conjunctival nevus has an intralesional cyst, which is a key differentiating characteristic from malignant melanoma as many other features overlap. The change in tumor size, increased pigmentation and corneal invasion are features suspect of malignant transformation and surgical excision and histologic examination are recommended for those lesions. Surgical excision for giant conjunctival nevus can cause several ocular complications such as symblepharon. Conjunctival reconstruction with amniotic membrane transplantation is useful for preventing complications.