Eye cancer. Coloured axial magnetic resonance imaging (MRI) scan of a patient's head showing a malignant melanoma (cancer) of the retina of the eye (orange). The nose is at upper left. The retina is the light sensitive membrane lining the back of the eye. It has become detached from the back of the eye here. Melanoma is a cancer of the melanocytes, pigment-producing cells in the skin. It is a highly malignant cancer, and can spread rapidly to other parts of the body (a process called metastasis). Treatment is surgical removal of the affected part of the body, often combined with radiation and drug therapy. Unless diagnosed early, the prognosis is poor.