Abstract: The present invention relates to a microfluidic device for the detection of circulating tumour cells (CTCs) in a fluid sample. The invention also relates to an in vitro method for the detection and/or quantification of circulating tumour cells (CTCs) in a fluid sample. Further, the invention relates to in vitro methods for (a) diagnosing a tumour and/or metastasis in a subject, and (b) determining the prognosis of a subject suffering from a tumour and/or metastasis. Finally, the invention refers to a kit comprising (a) a microfluidic device according to the first aspect of the invention, and (b) labelled probes targeting a first CTCs surface marker and, optionally, at least a second CTCs surface marker.