ABSTRACT
The revised WHO classification of hematolymphoid tumors introduced a category of nodal lymphoma with T follicular helper cell (TFH) phenotype, which includes angioimmunoblastic T-cell lymphoma (AITL), follicular T-cell lymphoma (FTCL), and nodal peripheral T-cell lymphoma with T follicular helper phenotype (PTCL-TFH) [1,2]. FTCL involves lymph node follicles resembling morphologically follicular B-cell lymphoma (FL). Both FTCL and PTCL-TFH were previously classified under the umbrella of PTCL. The WHO criteria specifically state that the expression of at least two TFH markers is required for the diagnosis of PTCL-TFH. TFH markers include CD10, BCL6, CXCL13, PD1 (CD279), ICOS, SAP (SLAM-associated protein), CXCR5, MAF (c-MAF), and CD200. AITL is the classic form of T-cell lymphoma of TFH origin, with diagnostic criteria that remain essentially unchanged from prior 2008 WHO classification. Both AITL and PTCL-TFH have similar phenotype, gene expression profile, and common mutation in TET2, DNMT3A, and RHOA genes [3–10]. Cutaneous T-cell lymphomas expressing TFH markers are excluded from this category (WHO).
