Extra- and intra-cellular digestion of elastic fibers by macrophages in annular elastolytic giant cell granuloma. An ultrastructural study.

A case of annular elastolytic giant cell granuloma was studied with the electron microscope using acid orcein stain. Elastic fibers were digested by multinucleate giant cells (MGCs) in 2 steps: the first step was the extracellular digestion and the second was the intracellular digestion. In the first step, the orcein-reactive amorphous materials of the elastic fibers surrounded by MGCs at first disappeared, and then the fine filaments appeared in elastic fibers. This process advanced in extracellular spaces of MGCs. In the next step, the fine filaments were phagocytosed by MGCs and were digested in phagocytic vacuoles.