Embodiments in accordance with the present invention relate to the use of effusive filtration to segregate tumor cells from a sample of bodily fluid. In one embodiment, fluid containing a cell is flowed down a channel having a filtration medium present along at least one side wall. The tumor cell is captured when the fluid passes through the filtration medium. Accumulated pressure on the captured tumor cell is reduced by allowing the fluid that has passed through the filtration medium to re-enter the channel. In a particular embodiment, the filtration medium may comprise side wall apertures having a width smaller than that of the cell, with downstream apertures allowing re-entry of the fluid into the channel.