Malignant melanoma of the choroid with balloon cells a clinicopathologic study of three cases.

We report the findings on clinicopathologic examination of three patients with balloon cell melanoma of the choroid. Ophthalmoscopically, all three had small, slowly progressive tumors at the posterior pole, with an encircling yellow halo. With fluorescein angiography, the yellow halo showed fluorescence similar to the remainder of the tumor, thus differentiating this substance from lipofuscin pigment, drusen and exudates. Light microscopy demonstrated prominent balloon cells which were most numerous at the tumor margins. These cells showed variable melanin pigmentation and were negative for lipid, acid mucopolysaccharide, and glycogen. Special enzyme studies (lactic dehydrogenase, succinic dehydrogenase, acid phosphatase, beta glucoronidase and aminopeptidase) demonstrated some similarity to melanocytic cells. Electron microscopy revealed premelanosomes and complex melanosomes in the cytoplasm of balloon cells without evidence of significant lipid.