Tapioca melanoma of the iris: clinicopathological correlation with results of fluorescein angiography.

A tapioca melanoma in a 75-year-old Caucasian man was shown by light microscopy to consist of spindle B cells with abundant vesicular cytoplasm, minimal pigmentation and surface nodularity that correlated with the gross appearance. Electron microscopy showed spindle shaped cells with multiple premelanosomes and melanin granules. Iris angiography demonstrated an irregular crisscrossing vascular network with a papillary configuration and fluorescein leakage confined to the tumour. The clinical appearance of the lesion and the angiographic findings are characteristic of this unusual variant of iris melanoma and help distinguish it from granulomatous iritis and from neurofibroma, leiomyoma and metastatic carcinoma of the iris.