Track: Case Reports

Abstract:

Granulomatous inflammation is an uncommon histologic pattern in subcutaneous panniculitis-like T-cell lymphoma (SPTCL), potentially mimicking infection, autoimmune panniculitis, or trauma. SPTCL typically affects younger patients; presentation in the elderly is rare and diagnostically challenging. An 82-year-old man presented with a thickened nodular plaque on the right arm with subcutaneous extension and overlying lichenification. Initial punch biopsy revealed mixed lobular and septal panniculitis with predominant lobular granulomatous inflammation, multinucleated giant cells, and adipocyte degeneration. Immunohistochemistry showed CD8 predominance over CD4, preserved CD2/CD5, slight CD7 diminution, negative CD56, and focal high Ki-67, raising suspicion for CD8⁺ T-cell dyscrasia/SPTCL. Months later, he developed new subcutaneous nodules. A new nodule on the left arm was biopsied for definitive evaluation. Histology revealed atypical subcutaneous lymphocytes with CD8⁺ predominance, TCR βF1 positivity, TIA-1⁺, granzyme B⁺ phenotype, and sparse CD20⁺ B cells; CD56, EBER ISH, and CD30 were negative. Ki-67 showed scattered increased proliferation. T-cell receptor gene rearrangement studies were equivocal but suspicious for monoclonality. Special stains for microorganisms and amyloid were negative. This case represents CD8⁺-predominant subcutaneous panniculitis-like T-cell lymphoma presenting with a prominent granulomatous panniculitis pattern in an elderly patient, an uncommon morphologic and demographic combination.This case underscores the diagnostic challenge of SPTCL in granulomatous presentations, the importance of repeat sampling, and the need for integrated histologic, immunophenotypic, and molecular correlation.

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Samantha Venkatesh