Sample Examination Management: Paraffin Embedding of Tissues
1.0 Purpose
To establish a standardized procedure for the paraffin
embedding of all processed tissues in the Histopathology Lab.
2.0 Scope
This SOP applies to all tissue samples processed in the
laboratory. It provides guidance to technicians on the proper embedding
procedure.
3.0 Introduction
The purpose of tissue processing is to embed tissue samples
in a solid medium that is firm enough to support the tissue and provide
sufficient rigidity for cutting thin sections, yet soft enough to prevent
damage to the knife or tissues. Paraffin wax is the most commonly used
embedding material for routine histology. The tissue must undergo several
preparatory steps before embedding in paraffin wax:
- Completion of fixation.
- Thorough dehydration to remove all water and aqueous
fixative from the tissue.
- Clearing with a substance compatible with both the
dehydrating agent and the embedding medium.
- Wax impregnation.
- Final embedding in paraffin.
4.0 Principle
Processed tissue samples are embedded in paraffin wax, which
provides the necessary support and rigidity for thin sectioning while being
soft enough to avoid damaging cutting tools or the tissue itself.
5.0 Analytical Measuring Range and Limit of Detection
Not applicable.
6.0 Responsibility
- Technical Staff
- Pathologist
7.0 Abbreviations
- NI: Not Indicated
8.0 Requirements
- Paraffin Wax: 58-62°C
- Instrumentation and Software:
- Forceps
- Scalpel
- Paraffin Embedding
Station: Leica EG1150H, EG1150C
- Disposables:
- Embedding Rings
- Embedding Molds
- Stationery:
- Marker Pen
All operations should be performed quickly to prevent
premature solidification of the paraffin wax.
Not applicable.
11.0 Documentation
Maintain the following records:
- Block Entry Register
- Temperature Logs
- 12.1.1 None.
- 12.2.1 Set the paraffin reservoir temperature to 65°C.
- 12.2.2 Open the cassettes containing processed tissue and
label an embedding ring with the sample number using a marker pen.
- 12.2.3 Place the embedding mold under the paraffin wax dispenser
and fill it with molten wax.
- 12.2.4 Use heated forceps to transfer the processed tissue
from the cassette to the embedding mold, positioning the tissue with the
cutting surface facing down.
- 12.2.5 Transfer the mold with the tissue to the cold plate
to start cooling.
- 12.2.6 Secure the pre-labeled embedding ring over the
mold.
- 12.2.7 Refill the mold with molten wax up to the rim.
- 12.2.8 Place the mold back on the cold plate for final
solidification.
- 12.2.9 Once the wax has set, remove the mold from the
embedding ring.
- 12.2.10 The tissue embedded in wax is now ready for
sectioning.
- 12.2.11 Maintain a daily temperature log of the embedding
station.
- 12.2.12 In case of a temporary breakdown of the embedding
station, manual wax pouring can be done. If the cold plate fails, blocks can be
cooled on ice or in a refrigerator.
- 12.3.1 Not applicable.
- 12.4.1 Retain paraffin blocks for 10 years at room
temperature.
Not applicable.
Not applicable.
Not applicable.
In case of reagent shortages, manpower issues, or equipment
breakdown, manual embedding can be performed as follows:
- 16.2 Open the cassettes containing processed tissue and label an embedding ring with the sample number using a marker pen.
- 16.3 Pour the melted paraffin wax into the embedding mold.
- 16.4 Slightly warm the forceps, then transfer the tissue
from the cassette to the mold, positioning it with the cutting surface facing
down.
- 16.5 Secure the pre-labeled embedding ring over the mold
and fill with melted wax up to the rim.
- 16.6 Allow the wax to set, forming a thin film on the
surface.
- 16.7 Cool the mold containing the tissue in wax.
- 16.8 Once the wax has set, remove the mold from the
embedding ring.
- 16.9 The embedded tissue is now ready for sectioning.
- Bancroft, J.D. *Theory and Practice of Histological
Techniques*, Fourth Edition.
END OF THE DOCUMENT
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