This paper presents a Lab-on-a-Chip (LoC) type MEMS scale non-invasive biosensor for detecting and differentiating tumor cells at single cell level based on their electrical properties. Presented device requires no cell labelling, cell stressing, cell immobilization or device functionalization. Device is composed of a microfluidic channel etched in silicon with semi-parallel micro-electrodes fabricated on channel sidewalls. Cells were detected by the impedance increase produced when they move along the channel and differentiated by analyzing impedance data at two frequencies. Device was tested with four human tumor cell lines and latex beads. Cells from all tested cell lines and latex beads were successfully detected and differentiation was demonstrated. Opacity was calculated to be 0.815, 0.201, 0.615, 0.275 and 0.1 for latex beads, MDA-MB-231 cells, MCF-7 cells, SK-OV-3 cells and ES-2 cells respectively. Thus, presented device possesses potential not only to detect, but also to differentiate circulating tumor cells in blood for diagnostic and research procedures.