Lupus profundus (panniculitis): a potential mimic of subcutaneous panniculitis-like T-cell lymphoma.

Lupus profundus is a rare manifestation of cutaneous lupus erythematosus, seen in 1% to 3% of patients. It most commonly presents in association with classic chronic cutaneous lesions of discoid lupus erythematosus; however, such lesions, as well as a clinical history of lupus erythematosus, may be lacking. The differential diagnosis for lymphocytic lobular panniculitides is broad; however, the consideration of subcutaneous panniculitis-like T-cell lymphoma is most critical. Recently, there have been several reports emphasizing the overlapping histomorphologic features between lupus profundus and subcutaneous panniculitis-like T-cell lymphoma. Although this is controversial, some authors suggest that patients with lupus profundus are at risk for the development of abnormal, clonal T-cell proliferations and/or overt subcutaneous panniculitis-like T-cell lymphoma. In cases of atypical lymphocytic lobular panniculitis that fail to meet diagnostic criteria for subcutaneous panniculitis-like T-cell lymphoma, patients should be clinically followed indefinitely, as future subcutaneous lymphoma cannot be excluded.