Flow Cytometric Enumeration of Peripheral Blood CD34+ Cells Predicts Bone Marrow Pathology in Patients with Less Than 1% Blasts by Manual Count.

Background and Aims: Significance of absolute number of CD34+ cells in the peripheral blood of patients with less than 1% myeloblasts by manual differential count is unknown and our aim is to study its relevance in clinical practice. Methods: We studied 138 peripheral bloods flow cytometric analyses in patients with less than 1% myeloblasts by manual differential, when CD34+ events were present in the gate that encompassed lymphocytes, monocytes, stem cells, and blasts. Results: The average absolute number of CD34+cells in the peripheral blood was 11 CD34+cells/µL ranging from less than 1 cell/µL to 147 cells/µL. The average absolute number of CD34+ cells in patients with an abnormal expansive process involving bone marrow (metastases, myelodysplasia, granulomas, marrow infections) or if bone marrow biopsy not performed, presumed expansive marrow process was 25 cells/µL, and in patients without an expansive marrow process (or presumed negative) was 4 cells/µL (P<0.00007). Cutoff 12 CD34+ cells/µL had 93% positive predictive value for bone marrow involvement by an expansive process and 78% negative predictive value. Conclusion: Flow cytometric testing of the peripheral blood is extremely sensitive method for enumerating CD34+ cells and can detect fewer than one CD34+ cell/µL. The absolute number of CD34+ cells in the peripheral blood is a useful parameter in determining marrow involvement by an expansive process and may provide guidance with respect to the necessity for bone marrow biopsy.

Nodal Marginal Zone Large B-Cell Lymphoma with Burkitt Translocation and Complex Chromosomal Changes Associated with Overexpression of BCL2, MYC, and BCL6.

We report the first case of a nodal marginal zone large B-cell lymphoma and the first with MYC rearrangement. This high proliferation rate lymphoma (40% of cells) occurred in the bilateral cervical, axillary, and para-aortic lymph nodes of an 82 year old woman. It involved extensively her bone marrow, and was lethal. Malignant B-cells were CD10 negative, harbored Burkitt translocation, and multiple chromosomal changes including trisomies of chromosomes 3 and 18, and three copies of 8q with an intact q24 cytoband (in addition to MYC rearrangement), associated with overexpression of BCL6, BCL2, and MYC respectively. We suggest that in aggressive nodular marginal zone lymphomas (clinical picture or high proliferation rate of lymphoma cells), fluorescence in situ hybridization analysis for MYC rearrangement, with break-apart probe, and for MYC/IGH translocation, in addition to chromosome analysis, should be performed. MYC rearrangement associated with a more rapid progression of the neoplasia, might warrant a more aggressive treatment.