Edge of lesions.
Wall of cysts.
Whole specimen if
Inking the Margins
To mark surgical
Spread of lesion
Different colors to
Specimen bits are
placed in porous
Not more than 5mm
In 10% formalin
~ 6 hour
Types of fixative:
Methanol and Picric acid.
A. Definition: removal of water
B. Rationale: for paraffin embedding/sectioning
1. wash out fixative
2. graded series of alcohol
70%, 95%, 100%, 100%
3. replace water by diffusion
4. not too long, not too short
• replacing the dehydrating fluid with a fluid that is totally
miscible with both the dehydrating fluid and the embedding
Choice of a clearing agent depends upon the
- Intended processing conditions such as temperature,
vacuum and pressure.
- Safety factors.
- Cost and convenience.
- Speedy removal of dehydrating agent .
- Ease of removal by molten paraffin wax .
- Minimal tissue damage .
is the process by which tissues are
surrounded by a medium such as agar,
gelatin, or wax which when solidified will
provide sufficient external support during
• 1. Place tissue cassette
in melted paraffin
• 2. Fill mold with
• 3. Place tissue in
• 4. Allow to cool
A. Orient tissue
1. cross section
2. longitudinal section
B. Dissection orientation
C. Avoid bubbles
Precaution while embedding in wax
The wax is clear of clearing agent.
No dust particles must be present.
Immediately after tissue embedding, the wax must be rapidly
cooled to reduce the wax crystal size.
There are four main mould systems and associated
embedding protocols presently in use :
• 1- traditional methods using paper boats
• 2- Leuckart or Dimmock embedding irons or metal containers
• 3- the Peel-a-way system using disposable plastic moulds and
• 4- systems using embedding rings or cassette-bases
Paraffin block with
consistency to cut
Paraffin blocks taken