A method for removing a tissue specimen from a patient includes introducing a bag at least partially into a cavity in the body of the patient, the bag comprising an open end and a port, positioning a tissue specimen to be removed from the patient into an interior of the bag by passing the tissue specimen through the open end of the bag, sealing the open end of the bag, removing gas from the interior of the bag through the port while the tissue specimen is contained in the interior of the bag, and entirely withdrawing the bag containing the tissue specimen from the cavity. The bag may include a closure device configured to hermetically seal the open end of the bag, and the port may include a one-way gas valve configured to prevent or retard gas from entering the interior of the bag through the port.