After the prefabricated receptor wax block is filled with the donor core, the slice is always cracked, is it the melting point of the wax block?

37 degrees usually only softens the conventional paraffin, and it is difficult to form a truly continuous interface between the donor core and the recipient wax block. It is recommended to incubate the filled wax blocks at 52-56 degrees for 30-60 minutes, the specific time is adjusted according to the size of the wax block, and do not exceed 60 degrees for a long time. More importantly, the melting point of the wax embedded in the donor tissue and the receptor wax block should be as close as possible. The supplier will generally mark the melting point of the receptor wax. If the melting point of your donor wax is low or high, the interface is prone to shrinkage cracks. You can first take the blank receptor block and the waste wax core for fusion testing.

Core filling pre-processing is often overlooked. If the outer diameter of the donor core is slightly smaller after sampling, and there are debris or uneven surfaces, it is not easy to fit even after heating after filling. It is recommended that the donor core be slightly tapered, the length of which is about 0.5mm shorter than the depth of the hole. Before filling the core, use a preheating probe to lightly press and discharge the bottom air. The mouse liver tissue itself is brittle, and the wax immersion should be sufficient when embedded, otherwise the donor tissue will fragment itself when sliced, and it looks like pore edge separation. If the donor wax block is too old or repeatedly melted, it is also easy to cause interface cracking.

Also troubleshoot the slicing session. Blunt knives, supercooled wax blocks, or too high a water temperature in the flap will enlarge the interface cracks. It is recommended to cool the wax blocks moderately on the cold table before slicing, replace it with a new knife, and slice it slowly and evenly. The water temperature of the spreader can be controlled at about 10-15 degrees below the melting point of the wax, not too high. Fetch a few pieces of HE to see the separation of the orifice edges. If only a few orifice edges are cracked and the tissue core is not removed, you can avoid them after marking; but IHC is best to choose a white sheet with a complete orifice edge, especially when quantifying or grading.

Cracked wax blocks can be remedied by first gently smoothing the surface of the wax block with a blade, dripping a small amount of melted paraffin into the visible area of the crack, selecting a wax with the same melting point as the acceptor wax or 1-2 degrees lower, and controlling the temperature below 60 degrees to avoid affecting the antigen. After dripping the wax, let it cool at room temperature, and then re-trim and try cutting again. If HE still sees the separation, it means that the fracture is not a slice artifact. It may be that the shrinkage rate of the donor wax block and the recipient wax block varies greatly. It is recommended that this batch of wax blocks should not be directly used for critical IHC, or no fracture slice should be preferred.