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What is Needle Aspiration?

Needle aspiration, also known as fine needle aspiration, is the most commonly used and least invasive diagnostic and biopsy method available. Fine needle aspiration involves using a needle to collect a sample of cells from a mass, lesion, or organ. Fine needle aspiration may also be used to collect a small sample of fluid in conditions where effusion – or fluid build-up – is present. The veterinarian will examine the sample using a microscope immediately after the sample is collected. 

However, any tentative diagnosis made using cytology must be confirmed by histological analysis. This means the sample must be sent to a laboratory and examined by a certified veterinary histologist. Results usually arrive within one to two days of examination.

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Needle Aspiration Procedure in Dogs

Needle aspiration is a quick and painless procedure. The approach to needle aspiration will vary based on the location of the condition. Ultrasound guidance is usually required to collect cell and tissue samples from internal organs. Sedatives or anesthesia may be administered to dogs that have lesions in sensitive areas, including the eyes and ears.

  1. The mass or lesion is cleaned.
  2. A fine needle with an empty syringe is inserted into the mass or organ.
  3. Suction is created when the plunger of the syringe is pulled back. This draws cells into the syringe and is known as aspiration. This process may be repeated several times to ensure an adequate sample is collected for examination.
  4. The cellular sample is transferred to a microscope slide and dried.
  5. A specialized dye is used to stain the slide so the cells show up clearly under the microscope.
  6. The veterinarian will then examine the slide under the microscope before sending it to a certified veterinary histology laboratory.

Efficacy of Needle Aspiration in Dogs

Fine needle aspiration is one of the most effective diagnostic and biopsy methods available today. It is also one of the least invasive diagnostic procedures, and causes virtually no pain for pets. In fact, the needle used for aspiration is typically thinner than needles used for vaccination. However, fine needle aspiration is not 100% effective. The effectiveness of needle aspiration ranges from 90.9% to 97.9%. The effectiveness of fine needle aspiration biopsy is 70% to 80%.

There is a chance that diseased cells will not be collected through fine needle aspiration. This applies particularly to certain types of cancer cells. While fine needle aspiration may help confirm some forms of cancer, other types of cancer cells – notably sarcomas – are more difficult to collect. This occurs because sarcoma cells do not easily exfoliate, or separate from the mass. Tissue biopsy is recommended to confirm a diagnosis of cancer.

Needle Aspiration Recovery in Dogs

Because it is a diagnostic procedure, dogs will not need to recover from fine needle aspiration. The veterinarian will contact the owner when the histology results come in – usually within one to two days – to determine the best course of treatment. If owners notice any changes in mass size or appearance, they should contact their veterinarian right away.

Cost of Needle Aspiration in Dogs

The cost of needle aspiration in dogs will vary depending on standards of living and additional treatment and diagnostic costs incurred. Fine needle aspiration is typically an inexpensive procedure which ranges in cost from $25 to $200. These costs may or may not include laboratory fees.

Dog Needle Aspiration Considerations

Needle aspiration is not recommended for dogs that have oral lesions or masses, since general anesthesia or sedation will be required to obtain a cell sample. In dogs with dermatological masses, all masses should be evaluated using fine needle aspiration. Sometimes, some skin masses can be benign while others are cancerous.

There are very few complications associated with needle aspiration. The main concern is misdiagnosis. However, misdiagnosis is incredibly rare, particularly if the pathologist and veterinarian are highly skilled. If the appearance of the aspirated mass changes significantly after aspiration, re-aspiration may be required.

Needle Aspiration Prevention in Dogs

Many conditions diagnosed by fine needle aspiration are difficult to prevent. Owners should make sure their dogs attend regular veterinary checkups so that underlying conditions can be diagnosed and treated quickly.

Needle Aspiration Questions and Advice from Veterinary Professionals

Jack Russell Terrier
6 Months
Moderate condition
1 found helpful
Moderate condition

Has Symptoms


My dog had an FNA and now the bump is more red than it was before. Is this normal? Before it was just pink like a light pink but now it is more red. The results revealed nothing as he couldn't pull any cells from the bump.

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
2159 Recommendations

Sometimes after the skin is punctured, there may be an increase in the colour of the surrounding area due to the body’s reaction to the ‘trauma’ which was caused by the needle or due to a small amount of bleeding caused by a damaged capillary. Generally these things are nothing to worry about and just keep an eye on it. Regards Dr Callum Turner DVM

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