Track

Case Reports

Abstract

Primary cutaneous peripheral T-cell lymphoma, not otherwise specified (pcPTCL-NOS), is a rare and recently recognized diagnostic category in the latest WHO classification. It represents one of the least common subtypes of cutaneous T-cell lymphomas and is characterized by aggressive clinical behavior. Molecular data on this entity remain limited.

In contrast, primary cutaneous CD30⁺ lymphoproliferative T-cell disorders are comparatively indolent and have been recently associated with TYK2 fusions.

We report the case of a 71-year-old female with a 3-year history of necrotic skin lesions. Biopsy revealed an atypical intermediate-sized lymphoid infiltrate involving the mid to deep dermis with subcutaneous necrosis, angiodestruction, and adipocyte rimming.

Immunophenotyping demonstrated expression of CD2, CD3, CD4, CD56, and cytotoxic markers (TIA-1, granzyme B), with a striking angiocentric growth pattern. There was marked downregulation of CD5 and CD7, absence of CD8, and rare CD30 expression (<1% of tumor cells). EBER in situ hybridization was negative. Tumor cells lacked surface T-cell receptor expression, and TCR gene rearrangement studies showed no evidence of clonality.

Molecular testing identified a TRAF1::TYK2 fusion, markedly increased JAK2 expression, and elevated PD-L1 mRNA. Additional low-level mutations were detected in MED12, TP53, TERT, MAP2K1, NOTCH3, and PIK3CA.

The patient was treated with involved-site radiotherapy and systemic gemcitabine-based chemotherapy, with no new lesions observed during six months of regular follow-up. This case highlights a novel molecular finding in pcPTCL-NOS with potential prognostic and therapeutic implications.