Abstract

Subcutaneous panniculitis-like T-cell lymphoma (SPTCL) is a rare lymphoproliferative disorder with a predominantly CD8+ cytotoxic phenotype, that typically involves the subcutaneous fat and presents as tender non-ulcerated deep-seated nodules. Constitutional symptoms are often present, and a subset of patients may develop hemophagocytic lymphohistiocytosis (HLH). On microscopy, SPTCLs show adipotropism with neoplastic lymphocytes rimming adipocytes leading to fat necrosis and karyorrhectic debris. Dermal mucin is not a common finding in SPTCL and has been reported only a handful of times with overlapping features of lupus erythematous. Here, we describe a diagnostically challenging case of SPTCL in a pediatric patient, who presented with fever, neutropenia, and year-long flesh-colored subcutaneous nodules. Initial biopsy showed abundant mucin in the reticular dermis and periadnexal inflammation, raising the possibility of juvenile cutaneous mucinosis. Subsequent biopsy showed similar findings with insufficient material to evaluate for panniculitis. The third and fourth biopsy demonstrated an atypical T-cell infiltrate suspicious for SPTCL, with most cells positive for Beta F1 by immunohistochemistry. Subsequent TCR gene rearrangement studies revealed clonal T-lymphocytic population for T-cell receptor-beta (TRB) locus. Bilateral bone marrow biopsies showed no involvement by lymphoma, but abundant hemophagocytosis, compatible with the patient’s clinical diagnosis of HLH. The patient was initiated on cyclosporine and prednisone, and reported an improvement in symptoms at their 2 month follow up with PET-CT showing markedly decreased multifocal soft tissue attenuation, consistent with metabolic response. This case highlights an atypical presentation of SPTCL in a pediatric patient, further understanding may lead to quicker diagnosis and treatment.