An assembly and method are disclosed for the filtration of a liquid and the use thereof, wherein a supporting body is designed in a recess of a carrier and a filter membrane lies flat on the supporting body. The filter membrane and the supporting body are designed to be permeable to liquids and thus serve as filters, in particular for filtering tumor cells from blood. The carrier can having standard shapes of an object carrier for microscopy and the filtration residue on the filter membrane can be easily handled and examined in the microscope. As a result of the filter membrane lying level on the supporting body, the filtration residue can be particularly well examined microscopically.