Refining Diagnostic Subtypes of Peripheral T-cell Lymphoma Using a Multiparameter Approach

Abstract

Peripheral T-cell lymphoma (PTCL) is a heterogeneous category, and many cases are unclassifiable and designated as PTCL-not otherwise specified (PTCL-NOS). Gene expression profiling (GEP) has delineated two prognostic subtypes within PTCL-NOS, PTCL-TBX21, and PTCL-GATA3, characterized by distinctive transcriptomes and a different prognosis. To further evaluate the pathologic features of these subgroups, 101 PTCL cases that did not meet specific criteria for well-defined T-cell lymphoma entities underwent detailed pathologic, immunophenotypic (including TFH biomarkers) and GEP analyses, separating them into PTCL-NOS (n=63) and PTCL-TFH (a.k.a. nodal PTCL-TFH, NOS, and TFH lymphoma, NOS) (n=38). PTCL-NOS cases were further categorized into PTCL-GATA3 (n=22; 34%) and PTCL-TBX21 (n=41; 66%), and a significant association (p < 0.02) with overall survival (OS) was reaffirmed. Histopathological assessment showed PTCL-GATA3 cases were characterized by monotonous medium-sized or large transformed cells with a minimal tumor microenvironment (TME) compared to PTCL-TBX21 cases, which consisted of pleomorphic cells in a polymorphous TME (p < 0.05). GEP analysis validated these TME distinctions. Immunophenotypic analysis showed that PTCL-GATA3 cases were predominantly CD4+CD8- and associated with significantly higher LEF1, MYC, and CD30 expression (p < 0.05). PTCL-TBX21 displayed a more diverse biomarker profile with two subgroups: one expressing cytotoxic antigens and enriched in CD8+CD4- or CD8-CD4- phenotype, and another lacking cytotoxic markers but showing a CD4+CD8- phenotype with increased ICOS expression, but devoid of other TFH markers. The PTCL-TFH cases correlated with an angioimmunoblastic T-cell lymphoma (AITL) gene signature, had more EBER-positive cells than the PTCL-GATA3 and PTCL-TBX21 cases, and a subset had some morphologic features of AITL (p < 0.01). This study highlights the unique morphologic and phenotypic variations within the newly-identified PTCL subtypes and should enable more precise diagnosis and tailored therapeutic strategies in the future.