a method of staging a tissue sample cassette , including a cassette body and a lid , from an upper position in a frame used during a tissue embedding process to a lower position in the frame . the method comprises coupling the cassette with the frame such that the cassette is in the upper position and positively stopped at the upper position by first structure on a wall of the frame . the cassette is moved relative to the frame to the lower position by selectively engaging the cassette with a staging mechanism . an external force is applied to the cassette with the staging mechanism in a direction to move the cassette from the upper position toward the lower position . the cassette is retained in the lower position using second structure on the wall of the frame , such that the cassette is exposed for embedding the cassette in an embedding medium and subsequently slicing the tissue sample embedded in the embedding medium .