Rheumatoid nodule – pathology

Histology of rheumatoid nodule

In a rheumatoid nodule, scanning power view reveals a granulomatous tissue reaction pattern (Figure 1). Well formed necrobiotic granulomas form within the dermis frequently with deep extension (Figure 2). There is a surrounding palisade of histiocytes and a mixed infiltrate of lymphocytes, plasma cells, multinucleated giant cells and occasional eosinophils (Figure 3).

Rheumatoid nodule – pathology

Special stains in rheumatoid nodule

Additional staining for fungal infections and mycobacteria should be considered in all significant granulomatous infiltrates.

Differential diagnosis of rheumatoid nodule

Deep granuloma annulare: The necrobiotic centres in rheumatoid nodules tend to demonstrate a bright eosinophilic consistency, whereas in granuloma annulare mucin deposition may be seen imparting a basophilic tinge.

Draft 14 February 2010