ACP5 and Ewing sarcoma: 24-h cultures of Ewing's sarcoma mononuclear cells on glass coverslips in the presence or absence of RANKL and M-CSF did not express the osteoclast markers TRAP and VNR but strongly expressed CD14, a macrophage antigen which is known not to be present on osteoclasts (Athanasou and Quinn, 1990; Athanasou, 1996).