Abstract

JL1 is a novel human thymocyte differentiation antigen, which is exclusively expressed by double positive (CD4+ CD8+) cortical thymocytes. We previously reported that the JL1 antigen was selectively expressed on the surface of acute lymphoblastic leukemia cells. T-Lymphoblastic lymphoma/acute lymphoblastic leukemia (T-LBL/ALL), the 6th prevalent lymphoma in Korea, is composed of immature neoplastic lymphoid cells and shows a rapid response to appropriate treatment. Early and precise diagnosis of LBL/ALL is crucial. Light microscopic distinction of LBL/ALL from other non-Hodgkin's lymphomas can sometimes be difficult and is aided by immunophenotypic studies. This study is designed to investigate the diagnostic utility of anti-JL1 monoclonal antibody (YG5) for LBL/ALL in formalin fixed, paraffin embedded tissue. We collected 25 cases of LBL/ALL (18 T-cell, 5 B-cell and 2 undetermined lineage) from 1993 through 1998. We confirmed the diagnosis using morphologic and immunophenotypic data. Strong JL1 expression along cell membrane was observed in 16 out of 18 T-LBL/ALL cases (89%). In 28 cases of other types of lymphomas of including 7 cases of non-T LBL/ALL and 14 cases of small round cell tumors, no JL1 expression was identified. These results show that the immunostaining for JL1 using YG5 on paraffin embedded sections can be useful for the specific diagnosis of T-LBL/ALL in routine diagnostic service.

• Keywords: JL1 antigen;Lymphoblastic lymphoma/leukemia;Immunodiagnosis;