Subcutaneous panniculitis-like T-cell lymphoma: a clinicopathologic, immunophenotypic, and molecular study of 22 Asian cases according to WHO-EORTC classification.

Subcutaneous panniculitis-like T-cell lymphoma (SPTL) is defined as a rare cytotoxic alpha/beta T-cell lymphoma characterized by primary involvement of subcutaneous tissue mimicking panniculitis and a predominant CD3+/CD4-/CD8+ phenotype in 2005 World Health Organization-European Organization for Research and Treatment of Cancer (WHO-EORTC) classification for cutaneous lymphomas. We presented a detailed study of SPTL, describing clinicopathologic, immunophenotypic, and molecular features of 22 cases in China. Strict diagnostic criteria according to the WHO-EORTC definition were applied to the diagnosis of all SPTL cases. Besides the common features described before, unusual CD4+/CD8- and CD4-/CD8- T-cell phenotypes were noted in 2 of our cases, respectively. CD30 was negative in all cases and CD56 was focally positive in 2 cases. Mortality in cases with angioinvasion (75%) was significantly higher than that in cases without angioinvasion (14.3%). Epstein-Barr virus (EBV) infection was detected in 1 immunocompetent patient by in situ hybridization. The frequency of rearranged TCRB, TCRG, and TCRD genes detected by BIOMED-2 multiplex polymerase chain reaction tubes was 80%, 67%, and 13%, respectively, with a total clonality detection rate of 100%. Clinical follow-up was available in 18 patients, ranging from 6 to 80 months. Most patients obtained complete or partial remission after therapy including one accompanied with EBV infection; 5 patients died: 3 of disease progression, 1 of severe infection, and 1 of complications caused by diabetes and hypertension. We conclude that SPTL as a cytotoxic lymphoma derived from alpha/beta T cell has a predominant CD4-/CD8+ phenotype, but unusual CD4+/CD8- and CD4-/CD8- phenotypes do exist. Owing to its indolent clinical course and relatively high survival rate, SPTL should be differentiated from cutaneous gamma/delta T-cell lymphoma. EBV is generally absent in SPTL but can rarely be detected especially in Asian population. Angioinvasion is a poor prognostic factor in SPTL.