TISSUE PROCESSING IN HISTOPATHOLOGY LAB
PREPARED BY MR. ABHIJIT DAS
Tissue processing in a histopathology laboratory is a
series of steps to prepare tissue samples for microscopic examination. The goal
is to preserve the tissue in as close to its original state as possible for
examination under a microscope.
STEPS OF TISSUE PROCESSING
1.
DEHYDRATION
Ø The
fixed tissue is gradually dehydrated by passing it through alcohol baths with
increasing concentrations: 70%, 80%, 90%, and
finally 100% ethanol.
Ø Each
step removes water from the tissue,
preparing it for embedding in paraffin wax.
Ø Dehydration
is essential since water is incompatible with the paraffin wax used for
embedding.
2.
CLEARING
Ø The dehydrated tissue is treated with a clearing
agent, like xylene, which removes the alcohol in
the tissue.
Ø Clearing makes the tissue translucent
and prepares it for infiltration with paraffin wax.
Ø This step is essential for ensuring the tissue is
ready for embedding.
3. INFILTRATION OR IMPREGNATION
Ø The cleared tissue is immersed in molten paraffin wax, which infiltrates and fills the tissue spaces.
Ø The wax provides support,
making the tissue stable for sectioning.
4.
EMBEDDING OR BLOCKING
OUT
Ø The
tissue is placed in a mold and covered with molten paraffin wax.
Ø The wax is allowed to cool and solidify, forming a solid block.
5.
SECTIONING
Ø The
embedded tissue block is cut into very thin slices,
typically 4-5 micrometers thick.
Ø These
thin sections are carefully placed on microscope slides.
Ø The
slides are then prepared for further staining and examination.
6.
STAINING
Ø The
tissue sections are stained with appropriate dyes to
highlight different structures within the tissue.
Ø Staining
enhances the visibility of various
components under the microscope.
Ø This
prepares the sections for detailed examination.