Identification of osteoclasts and their differentiation from mononuclear phagocytes by enzyme histochemistry.

A double staining method is presented which allows the enzyme histochemical differentiation between osteoclasts (mono- and multinucleated forms) and mononuclear phagocytes (macrophages, multinucleated inflammatory giant cells). Osteoclasts are characterized by a strong acid phosphatase activity whereas macrophages and inflammatory giant cells show a variable non-specific esterase activity. The described method may be useful in studying the osteoclast origin and the extraosseous distribution of these cells.