This antibody has value in classification of malignant lymphomas and acute leukemias, particularly for the identification of pre-B and pre-T acute lymphoblastic leukemia (ALL) / lymphoblasitic lymphoma (LBL). The intensity of Terminal Deoxyribo-nucleotidyl Transferase (TdT) expression is important since weak expression of TdT does not strongly support the diagnosis of ALL and LBL. This antibody may be useful when used in a panel of antibodies.