Conjunctival melanoma is a rare tumor that accounts for less than 2% of all ocular tumors, with an overall incidence of 0.24-0.8 cases per million. It can arise de novo (approximately 10% of cases), from a preexisting nevus (20%), or from the flat spreading pigmentation of primary acquired melanosis with atypia (60%-70%). Primary malignant melanoma of the conjunctiva is exceedingly rare. Conjunctival melanomas occur predominantly in individuals of Northern European descent aged older than 50 years and is rarely seen in other races and ethnicities.

Conjunctival melanoma spreads via lymphatics or hematogenously, and it may rarely extend into the orbit or globe. Metastases of medial tumors generally spread to the submandibular lymph nodes, while those of lateral masses spread to the preauricular lymph nodes. Metastases generally spread to the brain, lung, liver, skin, bones, and gastrointestinal (GI) tract. The rate of metastases for conjunctival melanoma is up to 26% by 10 years.

The overall tumor-related mortality rate for conjunctival melanoma is about 18%-25%. This rate increases to about 40% if the tumor arises from primary acquired melanosis with an intraepithelial pagetoid growth pattern. However, risk factors for death may also include a de novo melanoma without pathologic evidence of an associated primary acquired melanosis.