Describe the microscopic features of lupus panniculitis.

There is typically a mixed septal and lobular panniculitis with a predominance of lymphocytes in a patchy or diffuse and/or perivascular distribution. Nodular aggregates of lymphocytes surrounded by plasma cells may be present; there may even be formation of lymphoid follicles with germinal centers. Interstitial mucin deposition and hyalinization of the fat also occur. Overlying epidermal changes associated with cutaneous lupus erythematosus may be seen in close to one half of cases.

Ng PP, Tan SH, Tan T: Lupus erythematosus panniculitis: a clinicopathologic study, Int J Dermatol 41:488–490, 2002.