Unimeditrek SOP template — save it as PDF or print.
UNIMEDITREKTOTAL MEDICAL SOLUTIONS
SOP TEMPLATE Doc ref: UMT/SOP/TISSUE-PROCESSING Reviewed: July 2026 Rev.: template
Tissue Processing SOP
Histopathology · Unimeditrek Pvt. Ltd.
⚠️ Validation required. This SOP template is provided for educational and quality-system support only. It is a starting point to adapt — not a validated procedure. Each laboratory must review, complete the lab-specific fields, validate and approve this SOP through its own pathologist / quality manager, and align it with local regulatory requirements before use.
1. Purpose
To standardise the dehydration, clearing and paraffin infiltration of fixed tissue so that blocks section cleanly and slides stain consistently, with reproducible turnaround.
2. Scope
Applies to routine paraffin tissue processing of fixed histopathology specimens on the laboratory tissue processor. Excludes fixation (covered separately) and frozen-section work.
3. Responsibility
Histotechnician — loads cassettes, selects the validated program, starts/monitors the run and records reagent changes.
Labelled cassettes with adequately fixed tissue ≤ 3–4 mm thick
Reagent-change log and processing register
5. Safety precautions
Formalin, alcohols and clearing agents are hazardous — use in a ventilated/ducted area with PPE (gloves, coat, eye protection).
Follow local biomedical-waste and solvent-disposal rules; keep a spill kit accessible.
Confirm the processor lid/retort seals before starting a heated, solvent-laden cycle.
6. Procedure
Before the run
Confirm each specimen is adequately fixed before loading — under-fixed tissue will not process correctly. Minimum fixation time: [lab to validate] for your fixative and tissue types.
Verify tissue is grossed to ≤ 3–4 mm thickness; re-gross thick pieces rather than forcing a standard cycle.
Check reagent levels and position; confirm the reagent-rotation schedule is current.
Select the validated program for the load type (routine vs biopsy vs fatty/dense tissue). Cycle durations: [lab to validate].
Processing sequence
Dehydration through graded alcohols (ascending concentration) to remove water from tissue.
Clearing with xylene or a validated substitute to make tissue miscible with paraffin.
Paraffin infiltration under vacuum/pressure where available. Paraffin temperature: [lab to validate] (kept just above melting point; avoid overheating).
Run the program to completion; embed promptly after unloading to avoid over-hardening.
After the run
Unload cassettes and transfer to embedding without prolonged holding in hot paraffin.
Record run details, any alarms and reagent status in the processing register.
7. Quality-control checkpoints
Blocks are firm and section cleanly without shattering or a wet/soft centre.
Nuclei stain crisply on the resulting H&E slide (weak nuclear staining can indicate under-processing).
No excessive hardness/brittleness or chatter traceable to over-processing.
8. Acceptance criteria
Representative test block sections fully and stains with clear nuclear and cytoplasmic contrast.
No recurring processing-related defects across the batch.
9. Common errors & corrective action
Problem
Corrective action
Soft, wet, mushy tissue (under-processed)
Check fixation adequacy and tissue thickness; rotate/replace exhausted reagents; use an appropriate (not too short) schedule.
Hard, brittle tissue that shatters/chatters (over-processed)
Shorten the schedule or avoid long unattended holds; use a dedicated biopsy program for small specimens; verify paraffin/oven temperatures.
Inconsistent results batch to batch
Standardise the program per tissue type and enforce a reagent-management schedule with slide/section counts.