Autoimmune disease, including Lupus Panniculitis in association with Panniculitic Cell Lymphomas.

Some T cell lymphomas exhibit unique homing properties of the neoplastic lymphocytes for the subcutaneous fat. There are two primary forms of subcutaneous panniculitic lymphomas of T cell origin. The first falls under the designation of primary cutaneous gamma delta T cell lymphomas of the fat (PGD-TCL). The neoplastic cells are double negative for CD8+ gamma delta T cells and often have an aggressive clinical course. The other form of panniculitis, T cell lymphoma, falls under the designation of subcutaneous panniculitis-like T cell lymphoma (SPTCL). It represents a subcutaneous lymphoma derived from CD8+ T cells of the alpha-beta subset and typically has an indolent course. These two forms of panniculitic T cell lymphoma exhibit overlapping histologic features, with lupus profundus (LP) previously considered a form of panniculitic T cell dyscrasia. We present three cases of PGD-TCL of the fat in the setting of lupus erythematosus (LE) (two cases) and dermatomyositis (DM) (one case), respectively, whereby there were concurrent features of LE and DM in their lymphoma biopsies in two cases and prior biopsies compatible with LP which presaged the diagnosis of PGD-TCL by three years during which time the patient had a positive response to Plaquenil. One patient was diagnosed with PGD-TCL complicated by hemophagocytic syndrome after developing a lupus-like complex including certain supportive serologies such as antibodies to double-stranded DNA following initiation of statin therapy. The second patient presented with PGD-TCL and concomitant features of anti-NXP2 DM. The third patient presented in 2003 with LP and overlying skin features of acute LE, initially responding to Plaquenil, and then four years later was diagnosed with PGD-TCL, heralded by Plaquenil treatment resistance.  Two of the patients died from their lymphoma. All biopsies showed a characteristic histopathology of PGD-TCL. In two cases, the PGD-TCL was associated with overlying LE-cutaneous findings; another case had skin changes of lymphocyte-rich DM. In two cases, the MXA stain was strikingly positive, the surrogate type I interferon marker that is typically upregulated lupus erythematosus and dermatomyositis. There are eight prior reported cases describing SPTCL with concomitant cutaneous changes of LE, including six cases with an established history of LE, including LP responding initially to Plaquenil, similar to one of our cases. In the context of SPTCL or PGD-TCL, Panniculitis T cell lymphomas can be associated with concomitant clinical and histologic features of LE or DM, including an upregulated type I interferon signature. Identifying histologic features associated with an autoimmune diathesis should not be considered exclusionary to diagnosing any panniculitis T cell lymphoma. A clinical, histomorphologic, and pathophysiologic continuum appears between LP with SPTCL and PGD-TCL of the fat.