Objective  To explore the similarities and differences in clinical pathological features and gene rearrangement of lupus erythematosus profundus(LEP) and subcutaneous panniculitis-like T-cell lymphoma(SPTL).

  Methods  We compared the clinical presentations, histopathology, immunophenotypical features and T-cell receptor (TCR) gene rearrangement findings of 9 cases of LEP and SPTL.

  Results  For clinical features, most patients of LEP occurred on head and face without systemic symptoms. LEP patients responded well to hydroxycholorquine treatment with good prognosis. Most patients of SPTL tended to lower extremities involvement and accompanied with systemic symptoms, the patients with disseminated lesions or hemophagocytic syndrome(HPS) showed poorer prognosis. For histopathology, LEP patients showed dense inflammatory infiltrate in the dermis consisting predominantly of lymphocytes with less numbers of plasma cells. However, the dermis was spared in SPTL, and rimming of adipocytes and erythrophagocytosis was observed in SPTL. Lymphocytes of LEP expressing CD4⁺/CD8⁺, as well as clusters of CD20⁺. CD138-positive cells and scatter of CD123-positive cells were also observed in LEP. Tumor cells of SPTL were CD4^-/CD8⁺, βF1⁺, CD138^- and CD123^-. The expression of TIA-1 or GrB was more favor in SPTL. Monoclonal T-cell receptor-γ gene rearrangement was found in 89% of SPTL patients while negative for LEP.

  Conclusion  Base on different clinical and pathological features, it is easy to distinguish LEP from SPTL. However, a minority of lesions in LEP localize at subcutaneous tissue, which may turn to immunophenotypical and TCR gene rearrangement test for diagnosis.