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Primary Acquired Melanosis

a) What is primary acquired melanosis?

Primary Acquired melanosis (PAM) is newly formed brown pigmentation of the conjunctiva. People with white skin are more likely to get this. It usually affects one eye only. There are two different types of PAM: ‘PAM without atypia’ and ‘PAM with atypia.’ PAM without atypia is benign with no risk of transformation into melanoma. PAM with atypia, however, can turn into melanoma. Around 3 out of 4  conjunctival melanomas come from PAM with atypia. If you have dark skin, brown pigmentation of the conjunctiva from birth is very common and usually affects both eyes. This is known as conjunctival epithelial melanosis and is not likely to progress to melanoma.

b) What are the symptoms of primary acquired melanosis?

Uneven, painless, newly formed brown pigmentation is usually noted on the white of the eye. If the pigment is growing quickly or changing colour then it is more likely to be a conjunctival melanoma.

c) Am I likely to get primary acquired melanosis?

If you are middle aged and fair-skinned you are more likely to get primary acquired melanosis.

d) Will I need any tests to exclude melanoma?

If it is felt to be PAM without atypia we may take pictures in the clinic to help us monitor change. Sometimes a biopsy of the pigmented area, however, is needed to exclude cancer. When doing so we try to remove all of the pigmented area. The following features make us more likely to biopsy:

• Larger than 5mm

• Increasing in size

• Has thickened the conjunctiva

• Has a distinct nodule arising within it (pigmented or non-pigmented raised area)

• Has feeder vessels (blood vessels running into the pigmented area)

• Involving the cornea

• Involving the conjunctiva under the eyelids

• Previous melanoma

e) Is treatment needed for primary acquired melanosis?

PAM without atypia can be monitored in the clinic. The main treatment for PAM with atypia is surgery (surgical excision) with or without freezing therapy (cryotherapy) and Mitomycin C (MMC).