A cassette for retrieving plural tissue samples from a fluid stream. The cassette includes a bypass conduit and plural voids. A catch tray is removably seated in each of the voids. A fitting extends from the cassette. The cassette has an outlet opening through which a suction is drawn. The cassette also has a valve. The valve directs the fluid stream from the fitting so the fluid stream flows through the bypass conduit or through one of the voids in which a catch tray is seated.