Fig 2.

a Typical X-ray of a giant cell tumour in the distal femur situated in the epi- and metaphysis (growth plates are closed), b typical histology with multinuclear giant cells (MNGC, arrows) between numerous mononuclear cells without nuclear atypia (H&E stain, original magnification 200×), c a portion of the mononuclear cells (MNHC, arrows) reacts with an antibody against the histiocytic marker CD68 (original magnification 400×), d in this part of the tumour the MNHC are fused to the MNGC, the CD68-negative cells represent the neoplastic stromal cells (GCTSC, arrows, original magnification 400×)