Subcutaneous panniculitis-like T-cell lymphoma and lupus erythematosus profundus: a diagnostic dilemma

A white Caucasian woman in her 30s presented with an indurated lesion on her right upper arm. Panniculitis was clinically suspected. Antinuclear antibody testing was positive but incisional biopsy showed subcutaneous panniculitis-like T-cell lymphoma (SPTCL), although with some unusual features more in keeping with lupus. Initial treatment was with oral prednisolone and radiotherapy but with only partial response. A second biopsy was taken from an area of presumed residual disease. This displayed histological features that were much more typical of lupus erythematosus profundus (LEP) but with tiny foci suggesting concomitant microscopic areas of SPTCL. Immunofluorescence for IgM was positive. This case highlights the rare occurrence of a patient with overlapping clinical and pathological features of SCPTL and LEP. It emphasises the need for close clinicopathological correlation in the workup of patients with suspected panniculitis and the importance of careful pathological examination for features of both diseases.