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The peripheral T-cell lymphomas are a heterogeneous group of lymphoid malignancies each with a distinct clinical presentation and prognosis. The term "peripheral" denotes mature T-cell neoplasms, differentiating them from the precursor lymphoid diseases T-cell acute lymphoblastic leukemia and lymphoblastic lymphoma. Treatment regimens for peripheral T-cell lymphomas are generally derived from data extrapolated from trials of aggressive non-Hodgkin lymphoma (NHL) before the advent of CD20-directed therapies of which T-cell lymphomas represent approximately 10% of the studied population. While therapies are often overlapping, T-cell lymphomas in general have an inferior prognosis to their B-cell counterparts. Recent advances have been made, however, with development of treatments specifically directed at peripheral T-cell lymphomas.
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In 2012, there were an estimated 70,130 new cases of NHL in the United States with approximately 18,940 deaths (1). T-cell lymphoma is an uncommon subtype of NHL representing just 12% of all cases (2). The T-cell lymphomas have been subdivided by the most recent WHO classification scheme into predominantly leukemic, nodal, and extranodal variants (Table 35-1) (3). The International Peripheral T-cell Lymphoma project determined the relative frequencies and geographic variation of T-cell lymphoma of subtypes with peripheral T-cell lymphoma-not otherwise specified (PTCL-NOS) being the most common, followed by angioimmunoblastic T-cell lymphoma (AITL), anaplastic large-cell lymphoma(ALCL), and adult T-cell leukemia/lymphoma (ATLL) (Figure 35-1) (4). Notably, there are significant geographic differences in the incidence of these entities with PTCL-NOS being the most common in North America and Europe, whereas extranodal nasal NK T-cell lymphoma (ENKTL) and ATLL are more common in Asia due to the seroprevalence of the EBV virus and HTLV-1 viruses, respectively (Table 35-2).
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