Expression of CD31, cytoplasmic ADAM10 and activated Notch1 in multinucleated giant cells. In giant cell-rich osteosarcoma sections, CD31 expression was visualized with mouse anti-human monoclonal antibody (Ab), followed by fluorescein isothiocyanate (FITC)-coupled goat anti-mouse secondary Ab (green). ADAM10 and Notch intracellular domain (NICD) expression were detected by rabbit anti-human polyclonal Abs, respectively, and cyanine 3-coupled goat anti-rabbit secondary Ab (red). Nuclei of osteosarcoma cells were stained with 4′,6-diamidino-2-phenylindole (DAPI). Arrowheads in the merged pictures indicate colocalization of CD31/ADAM10 and CD31/NICD in multinucleated osteosarcoma tumor cells. Isotype-specific control immunoglobulin G (IgG) Abs were used to test staining specificity. ADAM10: A disintegrin and metalloproteinase 10. Scale bar, 20 μm.