Urgent Manual Paraffin Wax Processing
From time to time it is necessary to prepare a stained section for urgent diagnosis. Usually a frozen or cryostat section is used, but sometimes they are inadequate and a higher quality paraffin section is required.
Tissue Preparation
- Thickness: No more than 1 mm thick. Place directly into Carnoy’s fluid.
- Area: 10 mm × 20 mm.
- Unfixed tissue: This schedule was often used with fresh tissues when a paraffin section was needed for an urgent diagnosis.
- Times: All times in processing fluids for this schedule are for tissues 1 mm thick or less. Thicker tissues will not process.
- Clearing agent: Xylene should be used.
- Agitation: The gentle agitation, and a degree of warmth, required for this schedule was obtained by using a small container with a secure cap and putting it in a pocket, preferably close to the body. Natural movements and bodily heat were all that was required.
- Visual control: The tissue should be examined periodically to check progress, particularly when in the clearing agent as poor dehydration will show up as opaque areas.
- Processing time: This schedule requires about 4-5 hours to complete from tissue selection. The extra time in the first wax is required to bring the container up to temperature. The tissue should be gently blotted at each fluid change (except waxes) to minimize carry over.
Processing Schedule
- Trim tissue 1 mm or less and place into Carnoy’s fluid for 30 minutes.
- First absolute ethanol for 15 minutes.
- Second absolute ethanol for 15 minutes.
- Third absolute ethanol for 15 minutes.
- Fourth absolute ethanol for 15 minutes.
- Fifth absolute ethanol for 15 minutes.
- Sixth absolute ethanol for 15 minutes.
- First clearing agent for 15 minutes.
- Second clearing agent for 15 minutes.
- Third clearing agent for 15 minutes.
- Fourth clearing agent for 15 minutes.
- First wax at 58°C under vacuum for 30 minutes.
- Second wax at 58°C under vacuum for 15 minutes.
- Third wax at 58°C under vacuum for 15 minutes.
- Fourth wax at 58°C under vacuum for 15 minutes.
- Cast the blocks.
- Cool under iced water and section immediately.
Safety Note
Prior to handling any chemical, consult the Safety Data Sheet (SDS) for proper handling and safety precautions.
