Methods and Precautions for Paraffin Infiltration

Paraffin embedding is the most commonly used method in routine pathological work. The melting point of the paraffin used for embedding is generally around 60℃. In some cases, such as during certain enzyme stains, low-temperature paraffin embedding is required. In such instances, paraffin with a melting point of 52~56℃ should be used for embedding to preserve the activity of enzymes within the tissue.

Organizations of various sizes select embedding molds with corresponding base molds. During embedding, first note any special embedding surfaces (such as layered tissues, skin, and endoscopic biopsy samples, etc.). First, pour molten paraffin into the embedding mold, then gently pick up the tissue blocks already immersed in paraffin using a heated, curved,钝-nose forceps, ensuring the largest surface or the specified area of the tissue block faces down into the molten wax.

The tissue block should be placed flatly in the center of the embedding mold's bottom surface. The embedding surface must be level, and the embedding temperature should not be too high, otherwise it may cause the tissue block to scorch, affecting the diagnosis. For gastroscopy samples, multiple tissue blocks need to be packaged together. Place them vertically in the center of the embedding mold's bottom surface according to the mucosal surface (marking can be done in advance if necessary; generally, when the mucosal muscle is present, due to the contraction of the mucosal muscle, the tissue often takes on a horseshoe shape, with the convex surface being the mucosal surface. If the tissue block is flat, it can be embedded vertically). Multiple small tissue blocks embedded within the same wax block should be placed close together and flatly embedded on the same plane, ensuring no foreign matter is mixed in. The wall, skin, and mucosal tissues must be embedded vertically (standing embedding).

Place the embedding box on the embedding mold and fill it with wax twice.

Directly transfer the mold to the cold plate or into the embedding mold. After the surface of the molten wax has solidified, place the mold in ice water to accelerate the solidification. Remove the solidified embedding wax block (hereinafter referred to as the wax block) from the embedding mold, and use the wax trimming platform to remove excess paraffin around the wax block. Cautionary notes include:

The tissue blocks should be strictly embedded individually.

② Strictly prevent contamination from various foreign objects. Do not place unrelated tissues (including sutures, paper屑, or other foreign objects, especially hard ones) inside the wax blocks.

The embedding process should be carried out quickly to prevent the wax from solidifying before the tissue blocks are properly embedded.

The embedding wax for encapsulation should be pure and have an appropriate melting point (58~60℃).

⑤ When there are impurities in paraffin used for embedding, it should be filtered before use.

⑥ Do not overheat the forceps used for embedding, to avoid burning the tissue.