Fine-needle aspiration and tumour cytology
Sampling a tumour with a fine needle and examining the collected cells under a microscope — the quickest way to find out what a lesion is. Usually without sedation, often with a result on the same day.
What it involves
Fine-needle aspiration biopsy (FNA) involves inserting into the lesion a needle of a thickness similar to that used for vaccinations and collecting a small number of cells, which we spread on a slide, stain and examine under a microscope. The test can distinguish an inflammatory lesion from a neoplastic one, a lipoma from a mast cell tumour, and in many cases identify the type of tumour and its likely behaviour.
Cytology has its limits: it does not show tissue architecture or margins, and some tumours (especially sarcomas and some abdominal tumours) yield few cells. That is why an inconclusive result is not a failure — it is an indication for a tissue biopsy and histopathology. It is important to know this before anyone decides to remove a lesion “just in case”.
We sample not only skin lumps but also lymph nodes, lesions in the spleen, liver, kidneys and internal lymph nodes, and fluid from body cavities — in these cases under ultrasound guidance, which directs the needle to the right place.
When it is used
For any new or growing lesion in or under the skin, for enlarged lymph nodes, for changes in internal organs seen on ultrasound, and for fluid in the chest or abdomen. We do it before planning any procedure to remove a tumour — because the width of the margin and the extent of the operation depend on the type of lesion.
Indications: symptoms that should prompt a visit
- My dog has a soft lump under the skin and I want to know whether it is just a lipoma.
- A lesion on the skin changes size and colour within days.
- The lymph nodes under the jaw or behind the knees are enlarged.
- An ultrasound showed a nodule in the spleen or liver.
- My cat has an enlarged lymph node or a thickening of the intestine on ultrasound.
- The vet wants to confirm the type of lesion before planning an operation.
Conditions for which we use it in particular
Diagnostics beforehand
Sampling superficial lesions needs no preparation or preliminary tests. For internal lesions, we first perform an abdominal ultrasound, a blood count with a platelet assessment and basic clotting parameters, to reduce the risk of bleeding; the patient comes fasted, because we sample organs under short sedation.
How it proceeds
We sample skin and subcutaneous lesions in the consulting room without anaesthesia — it takes about 10–20 seconds, and the discomfort is comparable to a vaccination. We take 2–4 samples from different parts of the lesion to increase the chance of a representative specimen. We dry, stain and examine the slides in our laboratory; for lesions that need a second opinion, we send them to a cytologist (result in 1–3 days).
We sample internal lesions under ultrasound guidance and sedation with monitoring, after clipping the fur over the site. After the procedure we observe the patient for 1–2 hours and check with ultrasound for bleeding, after which the animal goes home.
Aftercare
After sampling superficial lesions there are no restrictions; a small bruise may appear at the puncture site. After a biopsy of internal organs we recommend a quiet day and observation — call if the animal becomes weak, turns pale or its abdomen swells.
We discuss the result by phone or at a visit and agree the next step straight away: observation, staging, surgery or a tissue biopsy.
Frequently asked questions
Can taking a needle sample “spread” the tumour?
With a fine needle the risk is negligible and many times smaller than the risk of operating without a diagnosis. We know the exceptions (for example bladder tumours) and take them into account.
Is a cytology result definitive?
For many lesions it is, but not for all. When the result is inconclusive or does not fit the clinical picture, we refer for histopathology.
How long does the result take?
With on-site assessment — the same day. With consultation with an external cytologist, 1–3 working days.
Does the dog need to be fasted?
Not for sampling skin lesions. For a biopsy of internal organs under sedation — yes, we will tell you when you book.
We manage every case individually. The scope, indications and course described above are indicative; we agree the exact diagnostic and treatment plan during the consultation. This content is for information only and does not replace a veterinary consultation.
Do you have questions about fine-needle biopsy and tumour cytology?
Call us or book a consultation. We will set out the diagnostic and treatment plan in writing, before you decide.