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Biopsy and Mass Histopathology

General guidelines

Site selection: certain sites require special approaches. For example, with splenic masses the most diagnostic site to sample is the margin between the mass and apparently normal spleen, since the centre is usually composed of blood. The soft areas of lytic bone lesions should be sampled rather than the bony periphery, which might only contain reactive bone. Try to avoid areas of marked necrosis; generous wedge biopsies can work well for most masses. Core biopsies are less likely to yield a diagnostic sample as they may not be representative.

Margin identification: you may use sutures or non-water-soluble inks to identify the margins. Allow the specimen to dry slightly or blot with tissue paper, gently apply ink sparingly over the entire surgical margins (avoiding any area you have sliced into) and blot the ink dry before placing the sample in formalin.

Tissue orientation: Under no circumstances should needles be used to identify specimens or to fix specimens to cardboard to keep them straight. If you wish to orientate a specimen, use sutures to tie to cardboard if required, or allow the specimen to dry slightly on cardboard over 30-60 seconds before putting it all in formalin.

Multiple samples: when submitting several lumps, place them in separate jars and label appropriately according to site; alternatively, ensure each tissue is clearly marked in some other way (e.g. sutures/ink) so that each specimen can be identified.

Sample handling: Skin tumours and other specimens in which surgical margins are to be evaluated should be kept as intact as possible. While we understand that you may wish to incise through the deep or lateral margin in order to assess the adequacy of excision at the time of surgery, this has the disadvantage of causing the margin to retract during fixation, making assessment of the margins difficult and sometimes impossible. Be careful not to crush the specimen with either your fingers or forceps. Do not squeeze samples into containers. Once fixed, they become firm and may be impossible to remove without cutting the specimen or the container.

Processing delays: if masses are very large or contain any bony tissue, there may be some delay in processing while we wait for the specimen to fix or decalcify.

Specimen:

Tissue

Container:

Screw-top plastic pots, and larger sealable buckets containing 10% formalin. The ratio of formalin to tissue should be 10:1.

Shipping Requirements:

All samples must be shipped in leak-proof, sealed containers with appropriate labelling (i.e. name, date, specimen/site).  Sample containers and shipping materials can be ordered from Gribbles Veterinary Pathology.