Embedding tissues in Paraffin Wax

procedure

1. Move tissues to the cassette bath. If the cassette bath is not filled with molten wax, it should not be filled with cassettes up to the top edge, as a film could form on the cassettes up to the top edge reducing the quality of embedding.
2. Make sure there are embedding molds in the mold warmer
3. Once started, all steps should be performed without delays to ensure the wax homogeneously solidifies in the mold, preventing layers, which could affect sectioning results or even promote weakness in the block.
4.  Open the tissue cassette carefully, check the number of pieces seen against the grossing log and initial beside the number of cassettes and pieces entered in the Embedding column to verify the correct number of tissue pieces are present.  If the number of pieces you see at embedding does not match the number of pieces submitted at grossing, a QA form must be filled out and submitted.
5. Select the appropriate mold. There should be sufficient room for the tissue with allowance for at least a 2 mm surrounding margin of wax. Use the smallest mold that will give you this margin.
6. Fill the bottom of the mold with paraffin and keep on the warmed surface.
7. Using appropriate warmed forceps select and orient the tissue, taking care that tissue does not cool in the air. Place the tissue in the wax/mold, orienting according to the type of tissue and/or special instructions from the grossing step.
8. Continuing to hold the tissue in place with forceps, move the mold to the refrigerated spot for a moment. Make sure to push the entire tissue surface to be cut onto the bottom surface of the mold. The tissue should now be oriented appropriately. If the wax becomes too solid the forceps will stick to the tissue. If necessary, a tamper can be used for tissues that are embedded with a ‘flat’ orientation.
9. Position the cassette base onto the mold, ensuring that it sits level on top.
10. Fill with paraffin (do not under or over fill the mold). There should be sufficient wax covering the bottom surface of the cassette, but not filled to the very top.
11. Place the mold on the cold plate to chill
12. Always wipe forceps between specimens to eliminate carryover (‘forceps metastasis’).
13. Once cool, remove the block from the mold and scrape excess hardened wax from the sides of the cassette.
14. Assess the quality of your work using the self-evaluation form.