Histopathologic and Immunophenotypic Features of Childhood and Adult Anaplastic Large-Cell Lymphomas

The t (2;5) (p23; q35) translocation associated with CD30-positive anaplastic large-cell lymphoma (ALCL) creates a hybrid gene encoding the chimeric nucleolar protein nucleophosmin-anaplastic lymphoma kinase (NFMALK) protein, which can be demonstrated by immunostaining with ALK1 monoclonal antibody. In this study, 40 specimens of ALCL from 6 pediatric, 34 adult patients, were immunostained with monoclonal antibodies against CD30 (Ber-H2), EMA, CD45 (LCA), CD3, CD20 (L26), CD15, and ALK1 antigens, and results were correlated with histopathologic features. The mean age of the pediatric and adult patients was 10-years and 38-years, respectively. ALK1 was positive in 14 cases (35%) representing 83% of pediatric and 26% of adult patients, statistically significantly higher in the pediatric group (p= 0.01). Considering the better prognosis attributed to cases with t (2;5), it is interesting to note that the percentage of ALK1-positive cases is significantly higher in pediatric patients with coexpression of EMA, compared to adults.