Occurrence of phenotypic abnormalities in CD34þ hematopoietic progenitor and precursor cells (HPC) and their major B-cell and nonlymphoid compartments has been frequently reported in myelodysplastic syndromes (MDS). Here, we analyze for the first time the numerical and phenotypic abnormalities of different maturation-associated subsets of bone marrow (BM) CD34þ HPC from 50 newly diagnosed MDS patients in comparison to normal/reactive BM (n ¼ 29). Our results confirm the existence of heterogeneously altered phenotypes among CD34 þ HPC from MDS and indicate that such variability depends both on the relative distribution of the different subsets of CD34 þ HPC committed into the different myeloid and B-lymphoid compartments, and their immunophenotype (for example, higher reactivity for CD117 and CD13 and lower expression of CyMPO, CD64 and CD65 on CD34 þ immature and neutrophil precursors), a clear association existing between the accumulation of CD34 þ HPC and that of immature CD34 þ HPC. Interestingly, expansion of erythroidand neutrophil-lineage CD34 þ cells is detected in low-grade MDS at the expense of CD34 þ plasmacytoid dendritic cell and B-cell precursors, while expansion of immature CD34 þ precursors occurs in high-grade MDS. On the basis of the number and severity of the phenotypic abnormalities detected, a scoring system is proposed that efficiently discriminates between normal/reactive and MDS CD34 þ HPC, the mean score significantly increasing from low-to high-grade MDS.

Key Points• Detailed characterization of myeloma circulating tumor cells shows that these represent a unique subpopulation of BM clonal PCs.• Myeloma CTCs are clonogenic, quiescent, and may represent an ancestral clone potentially driven by circadian rhythms.Circulating myeloma tumor cells (CTCs) as defined by the presence of peripheral blood (PB) clonal plasma cells (PCs) are a powerful prognostic marker in multiple myeloma (MM). However, the biological features of CTCs and their pathophysiological role in MM remains unexplored. Here, we investigate the phenotypic, cytogenetic, and functional characteristics as well as the circadian distribution of CTCs vs paired bone marrow (BM) clonal PCs from MM patients. Our results show that CTCs typically represent a unique subpopulation of all BM clonal PCs, characterized by downregulation (P < .05) of integrins (CD11a/CD11c/CD29/CD49d/CD49e), adhesion (CD33/CD56/CD117/CD138), and activation molecules (CD28/CD38/CD81). Fluorescence in situ hybridization analysis of fluorescence-activated cell sorter-sorted CTCs also unraveled different cytogenetic profiles vs paired BM clonal PCs. Moreover, CTCs were mostly quiescent and associated with higher clonogenic potential when cocultured with BM stromal cells. Most interestingly, CTCs showed a circadian distribution which fluctuates in a similar pattern to that of CD34 1 cells, and opposite to stromal cell-derived factor 1 plasma levels and corresponding surface expression of CXC chemokine receptor 4 on clonal PCs, suggesting that in MM, CTCs may egress to PB to colonize/metastasize other sites in the BM during the patients' resting period. (Blood. 2013;122(22):3591-3598) IntroductionIn the late 2000s, 2 pivotal studies elegantly showed that monoclonal gammopathy of undetermined significance (MGUS) precedes multiple myeloma (MM) in most, if not all myeloma patients. 1,2End-organ damage is the most important criterion to classify therapyrequiring MM patients, and the most common CRAB (hyperCalcemia, Renal failure, Anemia, Bone lesions) symptom is the presence of bone lesions detectable on a skeletal survey.3 Extramedullary disease is present in ;10% of newly diagnosed symptomatic patients, but it increases up to 20% in the relapse/refractory setting, 4 and typically anticipates a dismal outcome. Plasma cell (PC) leukemia is one of the most aggressive forms of the disease and even with novel drugs, the outcome is very poor with both short remission and survival rates.5 This landscape does not greatly differ from that of most solid tumors, in which the presence of metastasis is a key prognostic factor. 6 In fact, recent observations suggest that tumor cell dissemination is often an early event, 7 and the clinical sequel of circulating tumor cells (CTCs) has been the focus of extensive research. 8Interestingly, peripheral blood (PB) MM CTCs (morphologic and phenotypically defined as mature PCs) are also a common event throughout the spectrum of MM. [9][10][11][12][13] CTCs can only be detected in a small fraction of newly diagn...

A heterogeneous spectrum of immunophenotypic abnormalities have been reported in myelodysplastic syndromes (MDS). However, most studies are restricted to the analysis of CD341 cells and/or other major subsets of CD34 2 cells, frequently not exploring the diagnostic and prognostic impact of immunophenotyping.Methods: We propose for the first time an immunophenotypic score (IS) based on the altered distribution and immunophenotypic features of maturing/mature compartments of bone marrow (BM) hematopoietic cells in 56 patients with MDS that could contribute to a refined diagnosis and prognostic evaluation of the disease.Results: Although MDS-associated phenotypes were detected in reactive BM, the overall immunophenotypic profile of BM cells allowed an efficient discrimination between MDS and both normal and reactive BM, once the number and degree of severity of the abnormalities detected per patient were simultaneously considered in the proposed IS. Interestingly, increasingly higher IS were found among patients with MDS showing adverse prognostic factors and in low-versus high-grade cases. The most informative prognostic factors included the number of CD34 1 cells, presence of aberrant CD34 2 /CD117 1 precursors, decreased mature neutrophils and CD34 2 erythroid precursors, and increased numbers of CD36 2/lo erythroid precursors; in addition, the IS was an independent prognostic factor for overall survival.Conclusions: Assessment of immunophenotypic abnormalities of maturing/mature BM cells allows an efficient discrimination between MDS and both normal and reactive BM, once the number and degree of severity of the abnormalities detected are simultaneously scored. Interestingly, progressively higher IS were found among patients with MDS with adverse prognostic features and shorter overall survival.