Brown iris mass
The intensely brown mass is either a nevus (a benign collection of melanocytes) or a melanoma (a malignancy). Nevi are common; melanomas are rare. How can you tell the difference? Nevi do not usually grow very much.
This is a rare lesion and difficult to distinguish by inspection from the more common nevus. The recommended management is to observe for growth. If there is growth, the lesion should be biopsied.
Fortunately, the likelihood of metastasis is very low if the melanoma is confined to the iris. If it also involves the ciliary body, it poses more of a threat.
What to do?
Refer any patient who has a darkly pigmented mass on the iris, particularly if the patient has only recently noticed it or reports that it has grown.