Immunohistochemical characterization of pigmented villonodular synovitis.

Pigmented villonodular synovitis is made up of a variety of cells, including round or oval mononuclear cells, fibroblasts, synovial cells and multinucleated giant cells. The mononuclear cells were found to stain positively with anti-lysozyme, anti-alpha-1-antitrypsin, anti-alpha-1-antichymotrypsin and anti-fibronectin. Vimentin was detected in fibroblasts and in lining cells of the synovial membrane as well as in cells of acinus-like structures. The multinuclear giant cells contained lysozyme, alpha-1-antitrypsin and alpha-1-antichymotrypsin but no vimentin.