ABSTRACT
Introduction 678 Adult T cell leukemia/lymphoma (HTLV-1 related) 679 Clinical features 679 Histopathology 680 Phenotype and genotype 680 Genetics and pathogenesis 680 T cell lymphomas with predominantly nodal 681
presentation Angioimmunoblastic T cell lymphoma 681 Clinical features 681 Histopathology 682 Genotype and phenotype 683 Genetics and pathogenesis 684 Peripheral T cell lymphoma, not otherwise specified 684 Clinical features 685 Histopathology 686 Phenotype and genotype 687 Pathogenesis 687 T cell lymphomas with predominantly 689
extranodal presentation
Enteropathy-associated T cell lymphoma 689 Clinical features 689 Histopathology 689 Phenotype and genotype 690 Genetics and pathogeny 690 Hepatosplenic T cell lymphoma 691 Clinical features 691 Histopathology 691 Phenotype and genotype 692 Genetics and pathogeny 692 Subcutaneous panniculitis-like T cell lymphoma 693 Clinical features 693 Histopathology 693 Phenotype/genotype 695 Genetics and pathogeny 695 Cutaneous and mucosal γδ T cell lymphomas 695 Cutaneous γδ T cell lymphomas 696 Mucosal γδ T cell lymphomas 696 Key points 696 References 697
T cell lymphomas are a heterogeneous group of neoplasms with variable clinical presentations, morphologic patterns, phenotypes and underlying genetic abnormalities. They are divided into precursor T cell (lymphoblastic) neoplasms of thymic origin, and mature (peripheral) postthymic lymphomas. The latter are designated as peripheral T cell lymphomas (PTCLs), which account for about 10-15 percent of non-Hodgkin lymphomas in most Western countries, with a great geographic variation.1,2
Indeed, they are more frequent in Asia and their frequency varies from 1.5 percent in Vancouver to around 20 percent in Hong Kong.3 This may at least partly reflect the involvement of viruses in their pathogeny such as human T lym-
(EBV), whose presence is increased in some regions, especially in Asian countries.
