Septal granulomatous panniculitis: comparison of the pathology of erythema nodosum migrans (migratory panniculitis) and chronic erythema nodosum.

Fifty-eight cases of septal granulomatous panniculitis were reviewed; 14 cases were diagnosed as erythema nodosum migrans (migratory panniculitis) and 36 as chronic erythema nodosum on the basis of clinical and histopathologic features. Erythema nodosum migrans was characterized by markedly thickened and fibrotic septae, marked capillary proliferation (like granulation tissue), and massive granulomatous reaction (with giant cells) along the borders of the widened septa. Hemorrhage was rare, and phlebitis was not seen. Chronic erythema nodosum showed mild septal change, little fibrosis, and lymphohistiocytic perivascular inflammation with only focal granulomatous formation. Phlebitis and hemorrhage were common. The condition termed erythema nodosum migrans has many of the same clinical features as chronic erythema nodosum, and we think this term is preferable to migratory panniculitis. We believe that there are sufficient clinical and histopathologic features to justify considering erythema nodosum migrans as a unique clinicopathologic entity.