A method for treating a tissue sample including placing at least one tissue sample on an cassette which has: a retaining member, a base and at least one biasing element; placing the at least one tissue sample in the tissue cassette; attaching the base and the retaining member to retain the tissue sample; processing the tissue sample in the tissue cassette with one or more solvents; and embedding the tissue sample in a paraffin to form an portion of paraffin in which the tissue sample is embedded in the tissue cassette, wherein the embedding comprises adding molten paraffin to the interior area of the tissue cassette and allowing the paraffin to become solid.