Fig. 3

Electron microscopic findings. a, b Capillary endothelial cells show abnormal thickening of the subendothelial spaces containing collagen fibrils in a homogeneous matrix, fibroblast-like cells, and nonspecific vesicular structures. White arrowheads indicate Weibel-Palade bodies. c, d Smooth muscle cells with abundant accumulation of glycogen and myofilaments, as well as a few dense granules. Myofilaments are dispersed at the periphery of the cell along the cytoplasmic membranes. White arrows indicate myofilaments. e, f Epithelioid cells contained concentric membranous endoplasmic reticulum, numerous mitochondria, and cytoplasmic glycogen granules. Double arrowheads indicate mitochondria. g, h Adipocytic cells occupied by homogeneous osmophilic lipid vacuoles that are not membrane-bound. Black arrowheads denote lipid vacuoles. i Epithelioid cells contain myelin figures. Melanosomes were present in the epithelioid cells. Black arrows denote melanosome. Star denotes myelin features in a, c, e and g (low magnification). b, d, f, h, i High-magnification views