TRAP/DAPI staining of various histological types of osteosarcoma. The left panels show tartrate-resistant acid phosphatase (TRAP) staining of giant cell-rich, osteoblastic, fibroblastic and chondroblastic osteosarcomas, respectively. The right panels show 4′,6-diamidino-2-phenylindole (DAPI) staining of the nuclei of sections identical to those on the left panels. Note that negative TRAP staining was observed in multinucleated giant cells (upper panel). Dashed lines outline the cell contours. Scale bar, 20 μm.