Circulating tumour cells (CTCs) have recently evoked much interest in cancer research, representing potential prognostic biomarkers and a reliable mean to predict metastasis development. The presence of CTCs as a pre-requisite to develop distant metastasis is not a new concept, since it has been described by several scientists and physicians in the nineteenth century. However, only recently new biotechnologies able to correctly identify CTCs in cancer patients blood have been widely developed. For example, CellSearch (Veridex, LLC) based upon immunomagnetic technologies, constituted by magnetic nanoparticles coated with anti- EpCAM antibodies currently represents one of the best systems of CTCs detection. Thus since CTCs identification through CellSearch, before the beginning of a new line of chemotherapy, has prognostic value in breast, prostate and colorectal cancer, FDA approved the use of this type of methodology in these diseases (1).