Ultrastructure of elastofibroma.

An elastofibroma from a 69-year-old white man was studied by light and electron microscopy. The lesion was comprised of abundant collagen fibers and numerous randomly disposed masses of amorphous elastinophilic material. Ultrastructurally, this material appeared to be derived from a markedly dense, finely fibrillar precursor secreted by fibroblasts and manifested a striking resemblance to young elastic tissue. Central cores of mature elastic tissue were recognized within some of these elastinophilic masses. This study demonstrates unequivocally that the abnormal elastic material in elastofibroma is derived from excessive production of young elastic tissue and not from elastotic degeneration of collagen, as suggested in some of the previous studies. This young elastic tissue manifests a marked retardation of maturation, the cause of which however is not clear. Another interesting finding in this case was the presence of prominent fibrous laminae within the nuclei of most of the fibroblasts. The significance othis finding is briefly discussed.