Acute leukemia with coexpression of lymphoid and myeloid phenotypes

A multiparameter analysis of 706 cases of acute leukemia (AL) over a two-year period revealed only six cases (0.86 per cent) with coexpression of lymphoid and myeloid phenotypes. In three cases, expression of both lymphoid and myeloid markers by the majority of the blast cells suggested a 'biphenotypic' pattern while in the remaining three cases, the lymphoid and myeloid phenotypes were segregated into two morphologically distinct populations of blast cells indicating a 'biclonal' distribution. The poor response to anti-acute lymphoblastic leukemia therapy in five of these six cases underlines the bad prognostic significance of coexpression of lymphoid and myeloid phenotypes in AL. The incidence of 'mixed lineage' phenotype in the present series appears very low.