Standard procedures for preparing tissue specimens for microscopic examination involve multiple processes that end with the specimen infiltrated with paraffin, embedding the tissue specimen in paraffin wax, and sectioning the paraffin-embedded tissue specimen very thinly with a microtome. Typically, prior to embedding, the tissue specimen is treated by fixing, dehydrating, clearing, and saturating the tissue specimen with various fluids, including formaldehyde and water, ethanol, xylene.
Initially, a molten embedding material, such as a paraffin wax compound, is poured into a cavity of a mold to partially fill the mold cavity. The mold is moved to a cooling station where a bottom wall of the mold cavity is placed on a cooling rail to solidify or gel the paraffin in mold cavity. Next, the prepared tissue specimen is placed onto the gelled paraffin in the cavity of the mold. Positioning the tissue specimen onto the gelled paraffin involves orienting the tissue specimen to best present the specimen to the cutting blade of a microtome instrument. The tissue specimen is oriented such that consecutive cross sections produced from the tissue specimen show features of the tissue specimen throughout the tissue specimen. For example, a relatively long and thin tissue specimen may be oriented to extend substantially normal to a bottom wall of the mold cavity so that a healthcare provider can view the sequential cross sections and understand the features of the tissue specimen along its length.
Molten paraffin is then poured over the tissue specimen. A cassette or capsule having paraffin thereon is placed over the cavity in the mold and additional molten paraffin is poured over the cassette. After the paraffin solidifies, a cast block is formed that includes a base portion of the cassette or capsule and a paraffin block portion having the tissue specimen disposed within the block portion. In accordance with standard procedure, the size of various cassettes and capsules have been developed for processing tissue specimens, and have become relatively standardized so that the base portions of the cassettes and capsules are the specimen carriers to be placed within a chuck in a microtome sectioning device.
A common problem with using paraffin wax to embed a tissue specimen within a mold is that the wax sticks to the inner mold surfaces after cooling and resists removal of the embedded specimen casting from the mold. One solution to this problem is to treat the mold with a release solution, such as a soap-like solution, by spraying the mold with the release agent before pouring the paraffin into the mold. As will be appreciated, preparing a number of tissue specimens involves spraying each mold with the release solution which complicates and slows the process of preparing the tissue specimens. The complication caused by spraying each mold is especially acute in the context of production needs for efficiency when dozens or hundreds of embedded tissue specimens are required to be prepared. Further, with reusable molds, the release solution is typically applied each time the mold is used. The continual use of release solution increases the cost and difficulty of preparing tissue specimens and adversely affects the financial and environmental benefits of utilizing reusable molds.