[Amelanotic melanoma and nuclear magnetic resonance tomography--case report].

In MRI choroidal melanoma shows a very short relaxation time (T2), shorter than that of any other intraocular tumor. This short T2 time is referred to the high concentration of paramagnetic melanine in this tumor. Therefore, it is of interest to measure the relaxation time in an amelanotic melanoma and compare it with the histological analysis. The duration of T2 for the amelanotic melanoma examined ranged from 130 to 160 ms. The small concentration of melanine is not a sufficient explanation, but it is possible that there are some precursors of melanine with paramagnetic characteristics.