A filter support is releasably connectable to a tissue cassette for collecting and embedding cells in paraffin wax. The method includes providing a substrate with a surface that has a preselected pattern of adhesion sites located thereon. The filter assembly is constructed and arranged to provide, in its normal operating mode, a liquid flow path through the filter 32,33 in a first direction between the dirty water inlet 5 and the clean water outlet 6 and, in a cleaning mode, to provide a liquid flow path in a second direction between the dirty water inlet 5 and the sludge outlet 7.