[1][2][3][4] The test uses an in-vitro diagnostic system developed at INSERM, the Université Paris Descartes and Assistance Publique–Hôpitaux de Paris in order to isolate cancer cells from blood without loss and identify them through a diagnostic cytopathology-based approach.

A 1-ml sample of blood will typically contain 5 to 10 million leukocytes, 5 billion erythrocytes, and a small number of circulating rare cells, including: The diagnostic problem is to find and identify the rare CTCs among the abundant other cells in a given blood sample.

The ISET technology was first reported in 2000 in the American Journal of Pathology by the team of Professor Patrizia Paterlini-Bréchot.

Since the first report in 2000, over 80 scientific articles have been published using the Rarecells System verifying the findings of the initial developers.

In 2009 Metagenex gave back the licences of the ISET patents to its developers: INSERM, University Paris Descartes and AP-HP.