Ultrastructural and immunohistochemical features of coronal adenomas.

We studied by electron microscopy three coronal adenomas discovered incidentally in eyes removed surgically. Tumor cells displayed prominent intercellular interdigitations with numerous desmosomes, mitochondria, abundant rough endoplasmic reticulum, and nuclei with membrane infoldings and a granular chromatin pattern. In these characteristics, the tumor cells were identical to nonpigmented ciliary epithelium of the ciliary processes. These growths contained abundant extracellular material, which showed a dimorphic pattern of complex reduplicated basal lamina and granular areas without structure. Immunohistochemical studies on formalin-fixed, paraffin-embedded coronal adenomas demonstrated type IV collagen and laminin in the extracellular material. These findings confirm that coronal adenomas develop from nonpigmented ciliary epithelium and that the extracellular material of these tumors contains components normally present in basement membranes.