Rare Cells: Focus on Detection and Clinical Relevance

Abstract

The study of rare-cell populations is assuming a growing importance to the advancement of medical diagnostics and therapeutics. In several clinical studies, counting rare cells can provide valuable information on the status of the patient; examples are the search for circulating tumor cells in peripheral blood, tumor stem cells, endothelial cells, hematopoietic progenitor cells and their subpopulations, antigen-specific T-cells, invariant natural killer T cells, and fetal cells in maternal circulation. The study of rare-cell populations is useful not only to understand disease mechanisms, but also to find novel targets. With multiparameter capabilities and a very high analysis rate, flow cytometry is at present the most potent technology to address rare-cell analysis. This chapter will describe the main issues of the pre-analytical phase, including the amount of blood to use, the use of pre-enriched populations, the number of markers to use, and the number of cells to acquire. Moreover, we will discuss the importance of excluding doublets and the use of a DUMP channel, along with the importance of using optimal methodologies in all phases, including collection of biological samples, adequate controls, and expert use of software and hardware.