Understanding histology testing

(Aotea News, August 2010)

John McCafferty
Anatomic Pathologist

Why do histology specimens take several days to be reported?

For optimal processing even the smallest tissue piece requires at least six hours fixation, most of which is achieved through overnight processing of the tissue.

After overnight processing, the earliest a tissue section slide can be produced and viewed by a pathologist is around midday the day after specimen receipt.

If the case is relatively simple a report can be done at that time. However, many cases are complex and require further sectioning and/or special stains, which will add further days to the reporting time.

Please be patient for histology results, particularly in complex cases.

Who should I speak to about a histology test?

All specimens are assigned to pathologists based on a monthly roster. If you have a question regarding a particular case, contact the assigned pathologist through the Wellington SCL medical secretaries.

If the assigned pathologist is unavailable, it is possible for other pathologists to comment on the case. In complex cases, the assigned pathologist is in the best position to provide a final diagnosis as they have seen and described the original specimen. Other pathologists will only have a description of the specimen and the slides.

How can I help improve histology reporting

Clinical details are very useful and appreciated.

Correlation between the details and the histology findings can prevent irrelevant diagnoses being included in a differential diagnosis list that may be reported with a complex case. Please include clinical details with your histology requests and please use legible writing.

Please also ensure the specimen pot labelling is adequate and correct (including patient name and a further identifier such as date of birth, NHI and site of specimen). Reporting delays will occur if we need to confirm labeling.

Clear indication of the type of specimen is important:

  • The term “biopsy”, to pathologists, is usually regarded as sampling of part of a lesion — for example, incisional biopsy or punch biopsy.
  • “Excisional biopsy” is a poor term that can lead to confusion. If a lesion is removed in its entirety it is best termed an ‘excision specimen’ and the term biopsy should not be used.

Use orientation of specimens with sutures appropriately:

  • Orientation of specimens with sutures should be used only where a lesion present at a particular margin would result in a further limited excision.
  • Orientation of all specimens is not appropriate and creates additional work that will slow the reporting process.
  • A final reminder that, for the most part, punch biopsies of melanocytic lesions are not appropriate.

Why do we use formalin for fixation?

All tissues for routine processing require fixation to stop life processes degrading the tissue and preserve morphology.

Formalin is inexpensive and does a good job of fixation including compatibility with special stains.

Other fixatives are available but are not as good. This includes ethanol, which shrinks tissues and introduces artefact.

Specimens should be placed in a volume of formalin approximately 10 times the volume of the tissue.

There are certain special circumstances where tissue should not be put in formalin. These are usually specialist requests such as lymph node studies for lymphoma and cytogenetics in certain tumours, particularly sarcomas.

Specimens for gout should ideally also not be placed in formalin but rather at least a part of specimen should be fixed in alcohol.

Formalin is provided to practices in prefilled pots and in brown 1 litre bottles. These bottles can be reused so please return empty bottles to the laboratory for recycling rather than discarding them.

If there is doubt about whether to put a specimen in formalin please contact a histopathologist, or the histology department, for guidance.

Alternatively, leave the specimen fresh, don’t refrigerate and make sure the specimen reaches the laboratory within one to two hours. Any further delay will be detrimental to the specimen.

Please do not send fresh specimens at the end of the day.

Is direct immunofluorescence (DIF) available for skin biopsies?

We are able to perform DIF on skin biopsies (most useful in blistering disorders).

At least two biopsies should be performed, one of which can be placed in formalin and the other for DIF placed into DIF transport media. Please note that DIF cannot be performed on formalin fixed tissue.

The transport media is available from the laboratory. It should not be refrigerated and has a shelf life of about six months. The media is specially made for us and is limited in supply, so we will usually only provide one or two vials at a time.

What is a synoptic report?

A synoptic report is a list of relevant histological data about a case of malignancy. It usually follows and may replace the traditional descriptive microscopic report. It includes the minimum data required to further treat a patient.

Synoptic reports will usually be included with reports on melanoma, breast carcinoma and gastrointestinal malignancy.