Immunologic complexity of lymphoblastic lymphoma

Twelve patients with a histologic diagnosis of lymphoblastic lymphoma (LBL) were studied immunologically using the methodologic refinement of comparative serial section immunochemistry. By this means, we demonstrate complex LBL phenotypic profiles, revealing 3 major immunologic subtypes: immature T cell, 7 cases; intermediate or mature T cell, 3 cases; immature B cell (pre-pre-B), 2 cases. This phenotypic diversity challenges the basic belief that all LBL are the same. Our immature T-cell cases with frequent simultaneous Leu 2/3/6/9/CALLA/Tdt expression correspond to cortical thymic phenotypes; our mature T-cell phenotypes with Leu 9/la expression and absent L6/Tdt correspond either to medullary thymocytes or post-thymic T cells; our pre-pre-B phenotypes with simultaneous Tdt/CALLA/B4 expression correspond to common acute lymphocytic leukemia (ALL) phenotypes. Mature T-LBL phenotypes are similar to "novel" peripheral T-cell lymphoma phenotypes. Scant or absent Tdt expression in mature LBL is not an isolated antigenic change but a complete phenotypic profile difference from immature T-LBL. The major T- and B-cell phenotypes of LBL might have therapeutic significance. Treatment among LBL phenotypes may need to vary as with acute lymphocytic leukemia phenotypes. Further study is needed; in the meantime, comparative serial section immunotyping promises substantial utility in revealing the immunologic complexity of the lymphomas.