PMC5362881_01
Right atrium showing severe hemorrhage (formalin-fixed sample)
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No abnormalities were detected in the shape of the heart (Figure 1), and no significant changes were apparent in the other organs examined.
Arterioles are partially to completely filled with plump spindle cells that often form glomerulus-like arrangements within the lumens. Haematoxylin and eosin (x400)
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Within the nests of spindle cells, slit-like, narrow channels were present, occasionally containing erythrocytes and eosinophilic microthrombi (Figure 2).
Many intraluminal spindle cells stained positive for von Willebrand factor (vWF) antigen, which indicates endothelial cell histogenesis. Microthrombi also stain positive for vWF. Immunohistochemistry (x 400)
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Immunohistochemical analysis revealed that many intraluminal proliferative spindle cells were positive for vWF (Figure 3).
Arteriolar smooth muscle and some intraluminal cells (pericytes) stain positive for smooth muscle actin(SMA). Immunohistochemistry (x 400)
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Intense smooth muscle actin (SMA) staining was observed on the periphery of the intraluminal proliferations (arteriolar smooth muscles), and on some intraluminal cells (pericytes; Figure 4).