Multiparameter flow cytometry is necessary for detection, characterization and diagnostics of composite mature B-cell lymphoproliferative neoplasms.

Composite mature B-cell lymphoproliferative neoplasms are rare entities characterized by the simultaneous presence of two or more distinctive B-cell derived monoclonal malignancies. This retrospective study used multiparametric flow cytometric analysis aimed at immunophenotypic profiling of composite mature B-cell lymphoproliferative neoplasms in a cohort of 413 subsequent patients with de novo leukemic B-cell chronic lymphoproliferative disorders diagnosed in our institution during a 30-month period. Biclonality was found in 16 (3.9 %) patients. The vast majority (88 %) of the cases had one of the clones phenotypically corresponding to chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL). Only when composite cases were categorized by phenotype of the non-CLL/SLL malignant population did we find a statistically significant (P = 0.001) higher frequency of biclonality among cases with hairy cell leukemia (22 %). Biclonal cases had the overall B-cell membrane κ to λ ratio within the normal range (median, 1.9; reference interval 0.5-4.0), making recognition of malignancy somewhat challenging. Our analysis strategy was therefore based on the detection of aberrant B-cell phenotypes, with subsequent confirmation of the monoclonal nature of neoplastic clones with regards to light chain restriction analysis. Discrimination of the coexisting clones in biclonal cases was possible on the basis of the expression of other antigen(s) (63 %), light scatter properties (44 %), different surface light chain restriction (69 %) and/or pattern of expression (44 %). The most informative cell surface antigens proved to be CD22, CD20, surface IgM, and CD23. In conclusion, historic κ/λ ratio is not a reliable approach and is a poor measurement for the detection of composite lymphomas. More creative analysis techniques should be utilized for this purpose.

Epstein-Barr virus-negative aggressive natural killer-cell leukaemia with high P-glycoprotein activity and phosphorylated extracellular signal-regulated protein kinases 1 and 2.

Aggressive natural killer-cell leukaemia (ANKL) is a rare type of disease with fulminant course and poor outcome. The disease is more prevalent among Asians than in other ethnic groups and shows strong association with Epstein-Barr virus (EBV) and P-glycoprotein (P-gp) expression associated with multidrug resistance. Here we present a case of a 47 year old Caucasian female with a prior medical history of azathioprine treated ulcerative colitis who developed EBV-negative form of ANKL. The patient presented with hepatosplenomegaly, fever and nausea with peripheral blood and bone marrow infiltration with up to 70% of atypical lymphoid cells positive for cCD3, CD2, CD7, CD56, CD38, CD45, TIA1 and granzyme B, and negative for sCD3, CD4, CD5, CD8, CD34 and CD123 indicative of ANKL. Neoplastic CD56(+) NK-cells showed high level of P-glycoprotein expression and activity, but also strong expression of phosphorylated extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) MAP kinase. The patient was treated with an intensive polychemotherapy regimen designed for treatment of acute lymphoblastic leukaemia, but one month after admission developed sepsis, coma and died of cardiorespiratory arrest. We present additional evidence that, except for the immunophenotype, leukaemic NK-cells resemble normal NK-cells in terms of P-gp functional capacity and expression of phosphorylated ERK1/2 signalling molecule. In that sense drugs that block P-glycoprotein activity and activated signalling pathways might represent new means for targeted therapy.