Contribution on the ultrastructure of intraocular melanoblastomas.

The nucleoli and intercellular spaces were studied in 10 cases of intraocular melanoblastoma. The sizes of the nucleoli vary from 1.5-2.0 micrometer. The various nucleolar types seen in other tumours were also observed in melanoblastoma. The width of the intercellular spaces varied from 230 to 1,300 A. In the gaps ruthenium red-positive material was shown. In some of the cases this material exhibits a peculiar regular structure, the fundamental units of which are built up of filaments of the same size as found in the intercellular material of other places, however, more or less electron-dense periods alternate.