Subcutaneous Panniculitis-Like T-Cell Lymphoma Versus Lupus Erythematosus Panniculitis: Distinction by Means of the Periadipocytic Cell Proliferation Index.

The distinction between subcutaneous panniculitis-like T-cell lymphoma (SPTCL) and lupus erythematosus (LE) panniculitis is remarkably challenging. Rimming by lymphocytes with an elevated Ki-67 cell proliferation index has been forwarded as a potential diagnostic finding in biopsies of SPTCL but has not been rigorously compared with biopsies from patients with LE panniculitis. Nineteen and 17 examples of SPTCL and LE panniculitis, respectively, were evaluated for periadipocytic rimming by lymphocytes expressing Ki-67, CD8, and βF1 and for attributes associated with LE, including clusters of CD123-positive cells. The identification of periadiopocytic rimming using Ki-67, CD8, and βF1 held sensitivity of 79%, 100%, and 89.5% and specificity of 100%, 52.9%, and 88.2%, respectively (P < 0.01). CD123-positive cells were in both disorders. LE-like histopathology was commonly encountered in SPTCL. In conclusion, an elevated Ki-67 cell proliferation index with rimming is useful for distinguishing SPTCL from LE panniculitis. Notably, many features of LE panniculitis can also be encountered in SPTCL.