Acute leukemia with lymphoid/myeloid cell populations (hybrid leukemia). Case reports.

Based on conventional and immunological cell markers the great majority of acute leukemias can be classified as of lymphoid or myeloid origin. However, in some instances, leukemic cells with both lymphoid and myeloid features are found. For these cases the term of hybrid leukemia has been suggested; moreover, it has been shown that dual markers can be expressed by the same cell (biphenotypic leukemia) or myeloid and lymphoid cell populations coexist (biclonal leukemia). The accurate typing of acute leukemia is crucial in order to entail treatment and predict survival; therefore, the identification of acute hybrid leukemias may be important not only in terms of biological significance but also of management and outcome. We report here two further cases of acute hybrid leukemia with poor response to chemotherapy and very short survival.