Acute megakaryoblastic leukaemia with extreme thrombocytosis and p190(bcr/abl)rearrangement.

Acute megakaryoblastic leukaemia (AML-M7) is an uncommon disease, composing 0.5-1.2% of newly diagnosed adult acute myeloid leukaemias (AML). It is characterised by higher incidence and complexity of cytogenetic abnormalities. We report a rare case of Philadelphia (Ph) chromosome-positive AML-M7, presenting with extreme thrombocytosis and having a poor outcome. The diagnosis was established on the basis of morphological and flow cytometry data for megakaryoblastic proliferation in the bone marrow. Cytogenetics revealed 47,XX,+8,t(9;22)(q34;q11), and p190(BCR-ABL)-rearrangement was detected. MDR1-gene overexpression was not demonstrated; however, the patient was resistant to therapy and died in 6 months. The reported case contributes to the overt heterogeneity of Ph-positive AMLs, which warrants further investigation and understanding.

CD4+ acute undifferentiated leukaemia, probably early monoblastic type, developing in a patient with myelodysplastic syndrome and bone marrow fibrosis.

We report here a patient who presented with pancytopenia, hypercellular bone marrow and three-lineage dysplasia associated with an increase of reticulin fibres. After a 5-month period, anaemia and thrombocytopenia progressed very rapidly and the white blood count increased showing 45% blasts with monocytoid morphology, but cytochemically undifferentiated in nature. The immunophenotype revealed an unusual expression of CD4, CD36 and HLA-DR in the absence of any other myeloid or lymphoid lineage-associated markers. The patient died unexpectedly during the course of chemotherapy. The occurrence of CD4, CD36 and HLA-DR on the blast cells cannot determine the lineage of differentiation with certainty but provides some evidence that the leukaemic cells were probably derived from a very early monocytic progenitor with maturation arrest. These cells had apparently complex interactions with pathologic megakaryocytes and cytokine production.