Introduction:
Blood circulating endothelial cells (CECs) are cells which shed from the intima of the blood vessels into blood circulation in the course of cardiovascular diseases, cancers, infections, and inflammation. In healthy individuals, CECs are not present in peripheral blood or they occur at very low frequency. The presented report summarizes data about CECs, various clinical events with elevated CECs level and the methods of their quantification in the peripheral blood. CECs are thought to be a novel, reliable, non-invasive marker of vascular damage. CECs count is significantly increased in many pathological states connected with endothelial dysfunction, such as acute coronary syndrome, inflammatory vascular disorders, infections, diabetes, obstructive sleep apnea, and cancer. Clinical studies confirmed a positive correlation between the level of CECs and aggravation of the disease and its prognosis. In addition, CECs enumeration might be crucial for defining an appropriate treatment option for patients, also in anticancer therapy. There are the two main methods of quantification of CECs – immunomagnetic separation and flow cytometry. CECs count in the peripheral blood becomes helpful in clinical assessment of the activity of diseases, prognosticating their course and evaluation of the effectiveness of treatment. It is crucial to continue studies concerning the occurrence of elevated CECs count in various diseases and reach a consensus in the identification and enumeration of CECs.