Hand-mirror variant of acute lymphoblastic leukemia. Evidence for early T-cell lineage in two cases by evaluation with monoclonal antibodies.

Lymphoid cells from two patients with hand-mirror variant of acute lymphoblastic leukemia (ALL) were studied with various monoclonal antibodies in attempts to determine their derivation and differentiation. The predominant feature of the malignant bone marrow cells was strong reactivity with antibody 3A1, which stains the majority of normal T-cells and is apparently present on all T-ALL cells. In addition, a less intense binding was observed with antibody 4F2, which reacts with activated or rapidly dividing cells, and antibody 10.2, which reacts with all thymocytes and most peripheral T-cells. Most other antibodies with a wide variety of specificities were not reactive or, in the case of a few anti-T-cell antibodies showed, by fluorescence-activated cell sorter analysis only weak staining on some cells. Sequential bone marrow studies in one patient, before and during treatment with chemotherapy, revealed a reduction of 3A1-positive cells, concordant with a decrease of malignant cells in the marrow. When involved lymph nodes, peripheral blood, or marrow were studied, similar reactivity patterns were found in all locations. The data obtained suggest that in both patients with hand-mirror variant of ALL, the malignant lymphoid cells were immature cells of early T-lymphocyte lineage. The relation of phenotype by monoclonal antibody analysis to hand-mirror morphologic type and biologic function is discussed.