A catheter is provided with a collection chamber located between a seal and a cap. The seal is located distal from the collection chamber, and the cap is located proximal from the collection chamber. The seal may be opened and closed to alternately allow the passage of material into the collection chamber and prevent fluid from escaping from the shaft lumen. The cap may be opened and closed to allow the removal of a mass from the collection chamber and to prevent fluid from escaping during collection of the mass.
