Materials retrieved on the Filtrap. After the procedure, the net of the Filtrap was cut and fixed in formalin. The main samples captured on the net were stained with hematoxylin-eosin staining, special staining, and immunohistological staining. (a) Microscopic findings of main retrieved samples. (b) Hematoxylin-eosin stain: . The retrieved samples consisted of hypocellular deposits and were mainly composed of fibrin deposits with a few inflammatory cells (neutrophils). (c) Phosphotungstic acid hematoxylin staining (PTAH): . Fibrin deposits were confirmed by PTAH staining as blue. (d) Masson trichrome staining: . Fibrin deposits were also confirmed by this special staining as red. (e) Alcian blue staining: . Proteoglycans were only slightly detected. (f) Immunoreactivity to SMC α actin: . Smooth muscle cells were not detected in this material. (From JC Cases 5:e83-e86, 2012 with permission).