Track

Abstract

Primary cutaneous gamma-delta T-cell lymphoma (PCGD-TCL) is a rare, aggressive type of cutaneous T-cell lymphoma, making up <1% of cases¹. Under the 2022 WHO Classification of Hematolymphoid Tumors², there are two PCGD-TCL variants thought to have different cells of origin. The Vδ1 variant originates from upper skin layers, forming indolent subcutaneous plaques. In contrast, the Vδ2 variant originates from subcutaneous layers, forms rapidly progressive plaques, nodules, and tumors, and has a worse prognosis^3,4. A 33-year-old woman with no past medical history was admitted for diffuse, ulcerated cutaneous plaques with elevated liver enzymes, fatigue, pancytopenia, and chills. Her rash began 2 years prior and systemic symptoms 6 months prior. Skin biopsy demonstrated a predominantly dermal and subcutaneous atypical T-cell infiltrate with focal epidermotropism and adnexotropism.  The atypical T-cells stained positive for CD3, CD56 and TCR delta and negative for CD4, CD8, and CD5. EBER in situ hybridization was negative. The clinical and histologic features supported a diagnosis of PCGD-TCL, Vδ2 variant. Additionally, hemophagocytosis on histology and high clinically-determined H-score⁵ met criteria for secondary hemophagocytic lymphohistiocytosis (HLH). She began CHOEP chemotherapy and tocilizumab. PCGD-TCL portends a poor prognosis. The Vδ2 variant carries a 12.75-month median survival⁴ and increased risk of secondary HLH ^4,6,7. Given rapid disease progression and high mortality, it is critical for dermatopathologists to recognize and distinguish PCGD-TCL from more indolent processes like subcutaneous panniculitis-like T-cell lymphoma (SPTCL). In addition, PCGD-CTL’s more aggressive clinical course, epidermotropism, TCR delta positivity, CD5 loss, and cytotoxic marker expression can help with differentiation.