Fine structure of tapioca melanoma of the iris.

A case of a tapioca melanoma of the iris is studied by light and electron microscopy. Nodular elevations of the tumour were composed of spindle B- and epitheloid cells and of what appeared to be intermediate types. Tiny structures scattered over the entire tumour consisted of smaller epitheloid cells, many of which were found around superficial tumour vessels. Evidently, tapioca melanoma of the iris does not represent any specific histopathological entity. Tapioca melanoma of the iris is a low-grade malignant, locally aggressive tumour with a chronic clinical course.