The NK-cell associated antigen CD56 is expressed in 60-70% of cases, so many of these cases have an NK-like T-cell phenotype. 14, 15 Hepatosplenic lymphoma arises from an CD4 CD8 T cell or, in 15%, a CD4 CD8+ T-cell. 13 γδ T-cells are normally the first line of defense at epidermal and epithelial surfaces and they represent 10-12% of lymphocytes in the spleen. 9, 12 Most tumors have a γδ T-cell phenotype tumors arising from αβ T-cells are clinically and pathologically similar. Immunoperoxidase staining for T-cell antigens is important to aid in recognition. Marrow involvement is present in approximately two-thirds of cases but is usually subtle involving the sinuses. The presence of cytoplasmic granules is variable, but most report the cells are agranular. On Wright's stain the cells have partially condensed chromatin and pale blue cytoplasm. Circulating tumor cells are present in the blood in 25-50% or more of patients during the course of disease. 7–, 13 The tumor cells are homogeneous, medium-sized lymphocytes with partially dispersed chromatin, inconspicuous nucleoli and generally little cytologic atypia (Figure 1 see color page 547). Hepatosplenic lymphoma is an uncommon but distinct T-cell lymphoma with a characteristic growth pattern involving the hepatic and splenic red pulp sinuses. Post thymic T-cell and NK-cell neoplasms included in the REAL and WHO classifications are listed in Table 1. In addition natural killer (NK)-cell neoplasms have been recognized and are now formally included into the classification of lymphoid neoplasms. The REAL and WHO classifications have emphasized that extranodal lymphomas are intrinsically different from their nodal counterparts and have integrated clinical features (particularly site of disease) with more traditional pathologic criteria in defining these tumors. Most extranodal lymphomas were lumped together with nodal non-Hodgkin's lymphomas. The only extranodal lymphoma listed in early lymphoma classifications was mycosis fungoides/Sézary syndrome. Nowhere is this more evident than in the recognition of specific extranodal lymphomas. 1, 2 More importantly, these new classification systems have aimed to recognize specific clinicopathologic entities and not just be biologically correct. Similar to earlier functional classification systems (Lukes-Collins and Kiel), the Revised European American Lymphoma (REAL) and new World Health Organization (WHO) classifications have divided lymphomas into B and T cell types and whether they are composed of precursor (thymic or lymphoblastic) or peripheral (mature or post thymic) lymphocytes. He reviews therapy options for the extranodal subtypes of PTCL by drawing from series in adults, pediatrics, dermatology, and the Far East. He discusses the therapeutic options for anaplastic large cell lymphoma (ALCL), from a conservative approach for primary cutaneous ALCL to combination chemotherapy for the highly chemosensitive ALCL expressing anaplastic lymphoma kinase. Greer addresses whether PTCL should be treated differently from the more common diffuse large B cell lymphomas. Current management options and mechanisms of therapeutic response are also described.ĭr. The discussion focuses on LGL leukemia as an instructive model of dysregulated apoptosis causing both malignant and autoimmune disease. Loughran describes current understanding of the pathogenesis of large granular lymphocyte (LGL) leukemia. The use of ALK gene regulation in the classification of anaplastic large cell lymphoma is also reviewed.ĭr. Emphasis will be placed on extranodal T cell and natural killer (NK) cell lymphomas such as hepatosplenic lymphoma, subcutaneous panniculitis-like lymphoma and nasal/nasal type T/NK-cell lymphoma. Kinney gives a general overview of the diagnosis of PTCL and NK cell neoplasms. Additionally, their clinical behavior is variable and may not correlate with morphology.ĭr. Problems with PTCL include their rarity, representing usually 10-15% of non-Hodgkin's lymphomas in the Western Hemisphere, morphologic heterogeneity, and lack of immunophenotypic markers for clonality. This review covers the diagnosis and management of natural killer and peripheral T-cell lymphomas (PTCL).
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