Acute promyelocytic leukemia with T-cell markers and particular response to treatment. Report of a case

A case of acute leukemia with atypical malignant cells is reported. The clinical picture and coagulation studies were consistent with a disseminated intravascular coagulation syndrome. Morphologically, the leukemic cells from the peripheral blood and bone marrow showed azurophilic granules. More than 80% of cells were hypergranulated, resembling the macrogranular type of promyelocytes. Ultrastructural studies and the pattern of endogenous peroxidase were consistent with the microgranular type of promyelocytes in about 20% of the leukemic cells. Auer bodies were present in both types of atypical promyelocytes. Cytochemically, the whole malignant population exhibited intense peroxidase activity. Studies with monoclonal antibodies showed that about 45% of the proliferating cells expressed T-cell markers T3, T4, T8 and T11, but the cells were not reactive with OKM1 monoclonal antibodies. The chemotherapy for acute promyelocytic leukemia was inefficient, and the prompt disappearance of the blood abnormalities was observed only when chemotherapy for acute lymphoblastic leukemia was started. Therefore, it seems that in some cases of leukemia with hybrid types of malignant cells the morphological features determine the clinical picture, while the patient's response to the therapy is conditioned mainly by the cell surface phenotype.