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Antigenically defined subgroups of lymphoblastic lymphoma. Relationship to clinical presentation and biologic behavior

A large panel of monoclonal antibodies and polyclonal antisera were used to ascertain the immunophenotypic characteristics of 36 lymphoblastic lymphomas (LBL). Results showed that this group of lymphomas have significant immunologic heterogeneity. Of the 36 cases, 33 were positive for T‐cell antigens; among these, 22 cases were classified as T‐cell LBL (TLBL, Group 1) based on their expression of T‐cell‐restricted and T‐cell‐associated antigens, and five expressed the common acute lymphoblastic leukemia antigen in addition to T‐cell‐associated antigens (Group 2). Six cases showed strong reactivity with anti‐Leu‐11 antibody, which defines a specific subtype of lymphocytes considered to have a natural killer (NK) function (Group 3). Two additional cases had a “pre‐B” cell phenotype (Group 4), as determined by reactivity with BA‐1 and BA‐2 monoclonal antibodies, which react with immature and pre‐B‐lymphocytes. The neoplastic cells in the remaining case showed monoclonal surface membrane immunoglobulin of the IgMD heavy chain and kappa light chain type (Group 5). Despite immunophenotypic heterogeneity, the morphologic features were essentially similar in all cases. When the clinical features for each immunologic group were compared, however, two statistically significant findings resulted: (1) the frequency of mediastinal masses was highest in TLBL (Group 1, P < 0.01), and (2) the male–female ratio was significantly lower in patients with LBL expressing NK‐associated antigens (Group 3) than in the other groups of patients (P < 0.01). Our data indicate that LBL can be divided into several immunologic subtypes; larger, prospective clinicopathologic studies are required to determine the clinical significance of the immunophenotypic classifications of LBL.