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SOP templateTissue Embedding SOP (Template)
A ready-to-adapt template you can tailor to your laboratory. Complete the highlighted fields and validate before use.
Purpose
To cast firm, correctly-oriented paraffin blocks that section cleanly, presenting the diagnostically relevant tissue plane.
Scope
Applies to paraffin embedding of processed tissue at the embedding station. Excludes processing and microtomy.
Responsibility
- Histotechnician — embeds tissue with correct orientation and casts blocks.
- Senior technician — checks orientation and block quality; trains new staff.
- Pathologist / quality manager — approves this SOP and reviews re-embedding rates.
Equipment & materials
- Tissue embedding station (heated reservoir, cold plate, forceps warmer)
- Moulds, warmed forceps, labelled cassettes, molten paraffin
Safety precautions
- Molten paraffin and heated surfaces cause burns — use warmed forceps and care.
- Maintain ventilation; follow PPE and waste rules.
Procedure
Setup
- Confirm reservoir and cold-plate are at working temperature. Reservoir: [lab to validate]; cold plate: [lab to validate].
- Keep processed cassettes warm until embedded to prevent premature setting.
Embed
- Select the correct orientation for the tissue type (e.g. tubular/layered tissue on-edge to show all layers).
- Dispense molten paraffin into the mould, position tissue with warmed forceps, then transfer to the cold plate to set the orientation before topping up.
- Add the labelled cassette as the block base and top up with paraffin; allow to cool fully before removing.
Quality-control checkpoints
- Correct orientation for the tissue type; full-face sections achievable.
- No air bubbles or voids; block firm with tissue flat and complete.
Acceptance criteria
- Blocks section on the first face without re-embedding; orientation matches the grossing intent.
Common errors & corrective action
| Problem | Corrective action |
|---|---|
| Wrong orientation | Re-embed on the correct plane; mark orientation at grossing; use an orientation reference at the station. |
| Air bubbles / voids in the block | Embed with fully molten paraffin at the correct temperature; pour gently to avoid trapping air. |
| Tissue not flat / shifts before setting | Allow the cold plate to set orientation before moving; verify cold-module temperature. |
Records & documentation
- Embedding register / re-embedding log
- Corrective-action record
Review frequency
Review at least annually or after a workflow/equipment change or recurring re-embedding.
Related equipment & guides
Author: Unimeditrek Technical Content Team · Reviewed by: Unimeditrek Biomedical Engineering & Histopathology Applications team · Last reviewed: July 2026.
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