A group of ten patients with granulomatous panniculitis was studied; five had erythema induratum of the tuberculous or the nontuberculous type and five had erythema nodosum. In both groups, histiocytic giant cells and lymphocytic inflammation of the fat were seen microscopically. Massive caseation was seen in the patients who had erythema induratum, but this was not a distinguishing feature between the tuberculous and the nontuberculous type. The clinical history in all instances was a reliable guide to diagnosis. No specific cause was found, and treatment was not specific. In granulomatous panniculitis, the clinical pattern of disease is confusing in view of the histologic findings, and the diagnosis can be made with confidence only if the clinical findings are carefully correlated to the course of the disease.
Förström L, Winkelmann RK. Granulomatous Panniculitis in Erythema Nodosum. Arch Dermatol. 1975;111(3):335-340. doi:10.1001/archderm.1975.01630150055006