Elastofibroma: an in vivo model of abnormal neoelastogenesis.

Thirteen cases of elastofibroma have been studied by conventional light and electron microscopy, as well as by histochemistry and immunohistochemistry. By light microscopy elastinophilic material appeared as huge fibers crossing collagen bundles. Immunohistochemistry demonstrated a strong positivity for elastin in numerous and circumscribed areas of the extracellular matrix. By electron microscopy, collagen consisted of 40-50-nm wide fibrils, and elastin was made of large aggregates of moderately electron-dense material surrounding a very thin, apparently normal, elastin core. At high magnification these aggregates consisted of short tubules, often in regular arrays, surrounded by microfibrils and microfilaments. These data, associated with selective digestions on thin sections with elastase, purified collagenase, hyaluronidase, and chondroitinase ABC, revealed that elastic fibers in elastofibroma seem to be made of true elastin surrounded by an enormous amount of hydrophilic material, in which some elastin, chondroitin sulfates, and collagenase type-VII sensitive material are aggregated forming a rather ordered array of short tubules.