Fine Needle Aspirate Biopsies


Chris Belford BVSc MRCVS DVSc FACVSc


Fine needle aspirate biopsy FNAB is a relatively simple technique which can be carried out to provide more information on a lesion.

3 Steps to Successful FNABs

1.Lesion Selection

Discrete, definable lesions provide the best results. Oedematous, cystic, miniscule or extremely hard/fibrous (i.e. epulides) lesions may not provide many ar any cells. Cells are of course what cytology relies on!

2.Correct Sampling technique, preparation and speed

Speed of collection and sample preparation is very important to avoid microclotting of the cells. Samples should be prepared immediately on collection i.e. <0.5 seconds.

Here is the correct sampling technique and preparation:

Figure 1
Drawback and Push Away Method
Diagram of slide creation

Figure 2
Pull Apart Method
Diagram of Pull Apart Method

Samples are best taken from a couple of sites within a lesion as lesions are frequently not uniform. If the lesions are cystic, sample the edges of the lesions, do not sample just the cystic fluid which may contain few or no cells.

In the case of feline lymph nodes, vacuum should be kept to a minimum to prevent cell rupture.

In the case of firm/fibrous lesions vacuum should be increased and vigorous fanning performed to harvest adequate cells. Do not use a larger gauge needle as it usually increases blood contamination and needles larger than 21 gauge produce small core biopsies and not individual cells.

3.Provide an adequate history and lesion distribution/descriptions on sample submission for the cytologist.

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