A microfluidic device is disclosed. The device comprises at least one inlet for receiving circulating tumor cells and other cells in a sample; at least one curvilinear and/or spiral channel through which the sample is caused to undergo partial or complete Dean cycles to isolate the circulating tumor cells from the other cells; and at least one outlet configured to communicate with the channel for providing the isolated circulating tumor cells. The channel is configured to provide a predetermined Force ratio based on a desired threshold cell size of the circulating tumor cells. A corresponding method of manufacturing of the device, and a related diagnostic system are also disclosed.