[MIC2 (CD99) as a diagnostic marker for TdT-negative B lymphoblastic lymphoma].

Lymphoblastic lymphoma (LBL) is a rare hematologic malignancy that originates from immature lymphocytes and usually expresses terminal deoxynucleotidyl transferase (TdT). Here, we report a case of TdT-negative B-LBL. A 71-year-old male patient presented to a hospital with shortness of breath. His chest computed tomography showed a mediastinal mass. Tumor cells did not express TdT but expressed MIC2, which led to LBL diagnosis. MIC2 is a useful marker for LBL diagnosis.