Summary.
It has been possible to reinterpret non‐Hodgkin's lymphomas by applying subtle histological, cytological, and cytochemical techniques and electron microscopy as well as by using modern immunological methods and immune chemical analyses. This has led to the differentiation of four main groups of low‐grade and three main groups of high‐grade malignant lymphomas. Most non‐Hodgkin's lymphomas are derived from the B‐lymphocyte system. Only some of the lymphocytic, a small fraction of the lymphoblastic, and very few immunoblastic lymphomas originate from the T‐lymphocyte system. True reticulosarcomas are very rare and will have to be redefined.
Anaplastic large cell lymphoma (ALCL) is a subtype of non-Hodgkin's lymphoma characterized by the CD30+ large neoplastic cells and sometimes carries a t(2;5)(p23;q35). Recently, we found a novel hyperphosphorylated 80-kD protein tyrosine kinase, p80, in ALCLs with t(2;5). Subsequent cDNA cloning showed p80 to be a fusion protein of two genes, the novel tyrosine kinase gene and the nucleophosmin gene, in accordance with the sequence of the NPM/ALK gene (Morris et al, Science 263:1281, 1994). Meanwhile, the clinicopathologic features of p80-carrying ALCLs have remained unclear. Paraffin sections of 105 cases of ALCL were immunostained using anti-p80 antibody, and 30 of them were shown to express p80. Clinicopathologic comparison between p80-positive and -negative ALCLs showed that p80-positive cases occurred in a far younger patient age group (16.2 +/- 12.9 years; p80- negative cases, 51.0 +/- 22.3 years; P < .0001) and the patients showed a far better 5-year survival rate (79.8%; p80-negative group, 32.9%; P < .01). These data showed that p80-positive ALCL is a distinct entity both clinically and pathogenetically and should be differentiated from p80-negative ALCL.
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