[Magnetic resonance imaging in the diagnosis of doubtful cases of small melanoma of the choroid].

The main complementary procedures used to diagnose a choroidal melanoma are A- and B-mode ultrasonography, fluorescein angiography and magnetic resonance imaging (MRI). With MRI the malignant tumour has unique MRI signature owing to the paramagnetic properties of melanin. MRI can thus help in making the differential diagnosis and in estimating tumour extension. The advantage of MRI is that it provides complementary information that, when added to the results of the other investigative techniques, results in a quasi certain diagnosis. Three clinical cases are discribed.