Rheumatoid nodule in the oral mucosa. A case report with immunohistochemical study

A case of rheumatoid nodule in the buccal mucosa is reported. Histologically, 3 of zones characteristic rheumatoid nodules were recognized: a central necrotic area, an intermediate zone with palisading mesenchymal cells and an outer layer composed of chronic inflammatory cells. By immunohistochemical studies, ferritin was found in some of the cells in the intermediate zone, suggesting that these cells may be of histiocytic origin. Granuloma annulare and necrobiosis lipoidica may be differential diagnoses.