Abstract
Rheumatoid nodules developed on the finger tips of a patient with palindromic rheumatism. The patient had no bone cysts or erosions and had no rheumatoid factor. A light microscopic and ultrastructural study of a nodule showed a necrotic centre with fibrin, collagen, and granular material surrounded by large histiocytes, fibrocytes, lymphocytes, and vessels with adjacent mast cells as has been seen with nodules in classical rheumatoid arthritis (RA). We describe the first immunoperoxidase studies on a rheumatoid nodule and have identified reaction products for immunoglobulins and C3 in perivascular and endothelial cell vacuoles and in the necrotic centre.