Pathological and prognostic features of uveal melanomas.

Uveal melanomas may arise in the iris, ciliary body or choroid. Choroidal melanomas are the most common and usually display a discoid, collar-button or mushroom-shaped growth pattern. Uveal melanomas are composed of spindle and epithelioid cells and are classified histopathologically as either spindle-cell-type or mixed-cell-type tumours. The most important factors predicting clinical behaviour and underlying biology are cell type, cytomorphometric features, largest tumour dimension, scleral invasion and mitotic figures. Other valuable prognostic factors are tumour-infiltrating lymphocytes and macrophages, and the presence of vascular loops.