The lymph nodes are small glands situated throughout the body, with particular concentrations in the chest cavity and around the points where the limbs join the body. They are responsible for helping to regulate the immune system and dispose of waste products from the surrounding tissues. On occasion, these nodes can become compromised by any one of a number of health conditions and will cease to function properly. In order to determine the cause of the problem, the vet may choose to perform a biopsy, which is a procedure that will remove a tissue sample from the lymph node. This sample can then be used in laboratory testing to diagnose the issue that is affecting the lymphatic system. Note that most of the conditions diagnosed via biopsy tend to be localized to the lymph nodes themselves.

Prior to attempting the biopsy, the vet will conduct a number of imaging scans on the dog using ultrasound in order to precisely locate the gland and position the animal for the easiest access to the lymph node. Next, they will sedate the animal using general anesthesia and apply antiseptic to a small patch of the dog's skin before inserting the needle used to obtain the biopsy sample. The vet can guide the needle to the affected lymph node by using the ultrasound scans to see inside the body (typically if the node in question is located within the chest cavity) or by touch and visual observation alone (most common if the affected node is located on a limb or near the surface of the skin). Once the needle reaches the lymph node, it will be inserted inside and will grab a portion of the gland using the specialized prongs at the end of the instrument. At this point, the vet can remove the needle and allow the dog to wake up. In total, the procedure should not take more than a few minutes to complete.

The biopsy is one of the most effective means of obtaining an accurate diagnosis of a mass growing within the dog's body. This is because it allows the vet to directly observe the cells found in the growth under a microscope and perform additional tests, which can let them know exactly what is going on inside the inflamed lymph node. That said, it should be kept in mind by pet owners that the biopsy is not a treatment in itself, but rather a diagnostic method that can allow the vet to confidently recommend an appropriate course of action. Due to the procedure's invasiveness, some owners might be opposed to carrying out a biopsy. Instead, they will have to use imaging techniques such as CT scans and ultrasound to diagnose the problem. Unfortunately, these methods do not provide quite the same level of detail that can be obtained via a biopsy, so they are by no means exhaustive when making a diagnosis.

The vast majority of dogs will be back to normal within a couple of hours after the biopsy has been completed. Due to the use of a general anesthetic, some general drowsiness and loss of coordination may be noticed for the remainder of the day. Depending on the location of the node the sample is being taken from, the dog may experience some stiffness in nearby joints due to localized swelling around the path of the needle and the joint itself. Although the puncture wound from the needle is very small, owners should try to refrain from allowing the dog to become dirty being walked, due to the slight chance that they could pick up an infection.

Lymph node biopsies are relatively inexpensive procedures, with most commanding a price of under $300 (though this is dependent on the location of the target node and the age of the dog). Biopsies of nodes at the center of the body (where they are shielded by more bones and organs) can cost more, though this will differ on a case-by-case basis. By contrast, alternative diagnostic methods such as CT scan or ultrasound imaging have much different price points. A CT scan can typically be expected to be over $600 due to the level of expertise and specialized equipment required, whilst an ultrasound scan can cost as little as $100, depending on the equipment being used.

Whilst a lymph node biopsy is one of the most powerful diagnostic tool available for diagnosing a number of health conditions in dogs, it does come with some risks that could make some owners think twice about having the procedure done. Firstly, it requires the dog to be placed under a general anesthetic, which occasionally causes respiratory failure. Because of this, owners of older animals may have some concerns about conducting the biopsy. Secondly, because the biopsy needle is required to puncture the lymph node, there is a small chance that if cancer is present, this puncture will give it an opportunity to spread through the body. That said, the likelihood of this happening is especially small even if the specific type of tumor is prone to spreading.

Naturally, all dog owners will want to avoid their pet contracting the conditions that may necessitate a lymph node biopsy having to be carried out. Unfortunately, however, the vast majority of cancers that affect the lymphatic and adrenal systems are hereditary, and are impossible to predict without knowledge of the dog's parentage. Cysts, meanwhile, are far easier to prevent, mainly because the majority of cysts stem from bacterial infection. By maintaining a sanitary living area for the dog and making sure it receives a good quality diet, owners can significantly reduce the chances of this occurring.