High diagnostic value of morphologic examination and molecular analysis of bone marrow biopsies in a case of BCR-ABL+ CML with clusters of blasts.

We report a clinical case of chronic myelogenous leukaemia (CML) with regional B-lymphoblastic transformation. Peripheral leukocytosis of 160 x 10(9)/L, splenomegaly and fatigue suggested CML. In peripheral blood and bone marrow smears, white blood cells in all maturation stages and only few blasts were seen and therefore the diagnosis of chronic phase CML was proposed. Cytogenetics performed on peripheral blood cells revealed the characteristic t(9;22)(q34;q11) translocation as solitary abnormality. Analyzing the bone marrow biopsy a focal nodular B-lymphoid blast component was additionally seen. BCR-ABL FISH analysis demonstrated 31% atypical split signals in the B-lymphoid blasts and in the maturing myeloid cells, furthermore, BCR-ABL fusion transcripts were seen in the RT-PCR assay. Imatinib-based therapy led to temporary regression of peripheral leukocytosis. Bone marrow examination 3 weeks after therapy induction demonstrated considerably reduced cellularity and the proportion of B-lymphoid blasts had decreased to 20% of the nuclear cells. BCR-ABL FISH analysis still presented 21% atypical split signals but levels of BCR-ABL transcripts had significantly fallen indicating a rather favourable prognosis. However, 3 months after diagnosis the patient relapsed and developed an immunodeficiency with soor esophagitis and aspergillus pneumonia. A therapy with dasatinib was not successful and the patient died in consequence of immunodeficiency. This report demonstrates the high diagnostic value of bone marrow biopsy in the evaluation of CML. Besides morphology investigation of diverse methods including RT-PCR and FISH performed on diagnostic bone marrow biopsies are obligatory for ideal monitoring of drug response.