LMO2 Is a Specific Marker of T-Lymphoblastic Leukemia/Lymphoma

OBJECTIVES: The diagnosis of T-lymphoblastic leukemia/lymphoma (T-ALL) involving the thymus can be difficult to establish since neoplastic T lymphoblasts show significant phenotypic overlap with both normal thymocytes and thymocytes from epithelial thymic neoplasms (thymomas). LIM Domain Only 2 (LMO2) gene translocations have been implicated in the pathogenesis of a small subset of T-ALLs, and LMO2 protein has recently been reported to be expressed in a large proportion of T-ALLs. METHODS: In this study, we tested specificity of LMO2 for distinction between neoplastic and nonneoplastic T-precursor cells in thymus and bone marrow. RESULTS: Our findings show that LMO2 is expressed in neoplastic lymphoblasts of T-ALL and is absent in thymocytes of normal thymuses or thymomas. CONCLUSIONS: LMO2 is therefore a useful marker for immunophenotypic assessment of thymic neoplasms.