Peripheral T-cell lymphomas are a group of rare neoplasms originating from clonal proliferation of mature post-thymic lymphocytes with different entities having specific biological characteristics and clinical features. As natural killer cells are closely related to T-cells, natural killer-cell lymphomas are also part of the group. The current World Health Organization classification recognizes four categories of T/natural killer-cell lymphomas with respect to their presentation: disseminated (leukemic), nodal, extranodal and cutaneous. Geographic variations in the distribution of these diseases are well documented: nodal subtypes are more frequent in Europe and North America, while extranodal forms, including natural killer-cell lymphomas, occur almost exclusively in Asia and South America. On the whole, T-cell lymphomas are more common in Asia than in western countries, usually affect adults, with a higher tendency in men, and, excluding a few subtypes, usually have an aggressive course and poor prognosis. Apart from anaplastic lymphoma kinase-positive anaplastic large cell lymphoma, that have a good outcome, other nodal and extranodal forms have a 5-year overall survival of about 30%. According to the principal prognostic indexes, the majority of patients are allocated to the unfavorable subset. In the past, the rarity of these diseases prevented progress in the understanding of their biology and improvements in the efficaciousness of therapy. Recently, international projects devoted to these diseases created networks promoting investigations on T-cell lymphomas. These projects are the basis of forthcoming cooperative, large scale trials to detail biologic characteristics of each sub-entity and to possibly individuate targets for new therapies.

Linfomas T periféricos (PTCLs) compreendem um grupo heterogêneo de neoplasias que derivam das células linfoides pós-tímicas nos diversos estágios de maturação, com diversos padrões histológicos, fenotípicos, e clínicos. PTCLs são muito diversos entre si e refletem diversas células das quais foram originadas e são atualmente subclassificadas, usando-se a classificação da Organização Mundial da Saúde (OMS) 2008, apresentada neste texto na tabela 1. PTCLs compreendem 5%-10% de todas as doenças linfoproliferativas no mundo ocidental, com uma incidência global de 0.5 a 2 a cada 100.000 pessoas por ano e têm uma distribuição epidemiológica diversa com maior incidência na Ásia. Os achados clínicos dos PTCLs são muito heterogêneos. PTCLs expressam muito maior variação de apresentações clínicas do que os linfomas B, e há uma íntima, mas não absoluta, relação entre algum achado clínico não usual e certos subtipos histológicos. O autor faz aqui uma revisão do assunto altamente contemporâneo

Peripheral T-cell lymphomas (PTCLs) comprise a heterogeneous group of neoplasms that are derived from post-thymic lymphoid cells at different stages of differentiation and with different morphological patterns, phenotypes, and clinical presentations. PTCLs are highly diverse, reflecting the diverse cells from which they can originate and are currently sub-classified using World Health Organization (WHO) 2008 criteria. Peripheral T-Cell Lymphomas account for 5%-10% of all lymphoproliferative disorders in the Western hemisphere, with an overall incidence of 0.5-2 per 100,000 individuals per year, and have a striking epidemiological distribution, with higher incidence in Asia. The clinical features of PTCL are extremely heterogeneous. PTCLs express even more clinical diversity than B-cell non-Hodgkin's lymphomas, and there is a close, though not absolute, relationship between some unusual clinical features and certain histological subtypes.