Very little is known about the causes of conjunctival melanomas. It is possible that sun or UV exposure may be a factor in conjunctival melanoma, but there is no strong evidence to support this yet. Certainly conjunctival melanoma has more in common, biologically, with cutaneous melanoma (skin cancer) than it does with uveal melanoma, the most common eye cancer in adults.
The majority of conjunctival melanomas arise from pre existing condition of diffuse pigmentation called PAM (Primary Aquired Melanosis), although most cases of PAM are benign. It is therefore important that patients with PAM are carefully assessed. If melanoma is suspected, this is usually confirmed by looking at the tissue under the microscope.
Conjunctival melanoma can also arise from a previously existing pigmentation, known as a naevus. Naevi are common in the general population, like a mole on the skin, and only a small percentage will turn into malignant melanoma.
Occasionally conjunctival melanoma can appear from an unpigmented region and this is called “de novo”.
Rarely conjunctival melanomas may be non pigmented.