Track: Case Reports

Abstract:

Primary cutaneous gamma-delta T-cell lymphoma (PCGD-TCL) is a rare cytotoxic lymphoma that comprises less than 1% of primary cutaneous lymphomas and predominantly affects older adult males. While subcutaneous panniculitis-like T-cell lymphoma is strongly associated with autoimmune disorders and shares clinicopathologic overlap with lupus panniculitis, the link between autoimmunity and PCGD-TCL is much less established, particularly in the setting of anti-TIF1-γ dermatomyositis (DM). We report two cases of a TCR-delta positive T-cell lymphoproliferative disorder (LPD)/TCL arising in women with long-standing, immunosuppressed anti-TIF1-γ DM. Case 1 is a 47-year-old woman with a 19-year history of DM on azathioprine who developed rapidly progressive, painful subcutaneous nodules. Incisional biopsy confirmed a TCR-delta+, CD8+ cytotoxic T-cell LPD compatible with PCGD-TCL. She achieved complete remission following pralatrexate and subsequent allogeneic stem cell transplantation. Case 2 is a 27-year-old woman with DM on mycophenolate/rituximab who developed subcutaneous nodules with an indolent course and some spontaneous regression. A biopsy revealed a similar panniculitic infiltrate with an atypical TCR-delta+, CD8+ phenotype. Notably, next-generation sequencing in both cases was negative for high-risk JAK/STAT pathway mutations. These cases identify a γδ T-cell LPD as a potential complication in patients with anti-TIF1-γ DM on chronic immunosuppressive therapy. The shared, atypical CD8+ immunophenotype and absence of canonical driver mutations suggest a distinct pathogenic mechanism possibly linked to long-term immune modulation. Unlike classic PCGD-TCL, which is characterized by an aggressive course, the clinical courses in these cases arising in this anti-TIF1-γ DM were variable, with one requiring transplant and the other showing indolent behavior.

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David Fiorentino