The introduction in the clinical practice of several new approaches to
cancer immunotherapy has greatly increased the interest in analytical methodologies that can define the immunological profile of patients in the clinical setting. This requires huge effort to obtain reliable monitoring tools that could be used to improve the patient's clinical outcome. The clinical applications of flow cytometry (FCM) in oncology started with the measurement of
DNA content for the evaluation of both ploidy and cell cycle profile as potential prognostic parameters in the majority of human solid
cancer types. The availability of
monoclonal antibodies widely broadened the spectrum of clinical applications of this technique, which rapidly became a fundamental tool for the diagnosis and prognosis of malignant
hematological diseases. Among the emerging clinical applications of FCM, the study of
minimal residual disease in
hematological malignancies, the quantification of blood dendritic cells in various types of
tumors, the study of metastatic spread in solid
tumors throughout both the analysis of circulating endothelial progenitor cells and the identification and characterization of
circulating tumor cells, all appear very promising. More recently, an advanced single cell analysis technique has been developed that combines the precision of mass spectrometry with the unique advantages of FCM. This approach, termed mass cytometry, utilizes
antibodies conjugated to
heavy metal ions for the analysis of cellular
proteins by a mass spectrometer. It provides measurement of over 100 simultaneous cellular parameters in a single sample and has evolved from a promising technology to a high recognized platform for multi-dimensional single-cell analysis. Should a careful standardization of the analytical procedures be reached, both FCM and mass cytometry could effectively become ideal tools for the optimization of new immunotherapeutic approaches in
cancer patients.