Problems and Solutions in Histological Technique

Problems in Histopathological Technique

Prepared by

ROY ELLIS

IMVS Division of Pathology

The Queen Elizabeth Hospital

Woodville Road, Woodville, South Australia 5011

Email: roy.ellis@imvs.sa.gov.au

PROBLEM NUMBER 10

Wrinkled or compressed sections

These are caused by:

a Blunt knife. Blunt knives do cause many problems and if your knife is blunt the section will wrinkle because of the different densities between the wax and tissue and the different densities of the components within the tissue. The different densities offer a range of conflicting forces at the knife edge all of which cut at different rates if the knife is blunt causing those dreaded wrinkles.
a warm block
or knife have similar effects. A harder, colder material can be cut with less friction than soft, warm material if the knife is sharp. The softer, warmer material will wrinkle more easily.
If a Clearance angle is too great there is far more friction as the block meets the edge of the knife which causes some compression and wrinkling.
a Loose knife can cause all sorts of problems, wrinkling and compression being only two of them. The most serious problem with a loose knife would be the blade digging deeply into the block destroying the block face. If your lucky the tissue will not be destroyed in the process and can be re-blocked. If your not lucky you may destroy the architecture of the tissue. So make sure that your knife is held firmly in place.
Incomplete dehydration which increases frictional forces within the tissue because the tissue is softer and more rubbery. Sections are difficult to cut and are often wrinkled.
Soft wax has the same effect as a warm block
If the Bevel of knife is too deep making the cutting angle too shallow the effect is the same as having a clearance angle too great. There is far more friction as the block meets the edge of the knife which causes some compression. This is only a problem if you are still re-sharpening the old style solid knives. It is not a problem with disposables.
And the Micrometer set too thin for hardness of wax. What usually happens when you try to cut a section that is too thin for the wax you are using is that the section crumbles. But wrinkling is also one of the symptoms of having the micrometer set too thin for the wax type being used. And there are many wax additives which can change the characteristics of paraffin wax - like adding stearic acid to make paraffin wax harder.
- Or piccolyte 115 to help sections flatten
- Or plastic polymers to improve adhesion
- Or beeswax to make wax softer and stickier
- Or DMSO to aid in thin section cutting

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