Injection-Site Sarcoma Average Cost

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What is Injection-Site Sarcoma?

ISS tumors are firm growths underneath the skin that may start off small and continue to grow. Once the tumors are present, cancer can easily spread to other parts of the body. The quicker you bring your cat to a veterinarian for treatment, the better chance he has of surviving.

Vaccines and other injections used to administer medication are intended to protect your cat, but sometimes, they can lead to a very serious condition known as injection-site sarcoma (ISS). ISS is tumor growth that occurs at the site of an injection weeks, months, or years later. These tumors usually develop as a result of rabies or feline leukemia vaccines, however, any injection could cause them. Cat owners should frequently monitor injection sites including the legs and shoulder blades to check for any unusual growths.

Symptoms of Injection-Site Sarcoma in Cats

The main symptom of an injection-site sarcoma is a tumor, or mass, around the location of the injection. But, it’s important to note the tumor can form long after the injection took place. Most tumors form within a few weeks, but they can form up to 10 years after the initial injection. The tumors are usually firm and located in injection sites between the shoulder blades or on the rear legs.

Causes of Injection-Site Sarcoma in Cats

Although it is rare, it’s possible for a tumor to develop at an injection site. These tumors are most often linked to vaccinations, but they can occur after any type of injection. It’s unclear why these tumors form, however, many experts believe some cats are genetically predisposed to this condition.

Diagnosis of Injection-Site Sarcoma in Cats

If you notice any lumps on your cat, bring him to a veterinarian right away. Let your vet know when you first noticed the lump, and also give him a background of what vaccinations and injections the cat had in the past. Remember, tumors can take years to form, so it’s important to tell your vet about every injection your cat has had, not just the most recent ones.

Once you have discussed your cat’s symptoms, the vet will need to begin diagnostic tests. Needle aspirates are usually used to diagnose injection-site sarcomas. This involves inserting a small needle directly into the tumor to remove cells for testing. However, this test is not always accurate, so a biopsy may need to be performed to confirm a diagnosis. Vets usually follow the 3-2-1 rule when deciding whether a biopsy is needed. This rule states a biopsy is needed if the tumor has been present for at least 3 months, is wider than 2 cm in diameter, or if it increases in size after 1 month.

If the biopsy shows the tumor is cancerous, the vet may also perform a complete blood count and urinalysis test to determine if the cancer has spread. X-rays of the abdomen and chest may also be done.

Treatment of Injection-Site Sarcoma in Cats

Your cat will need to go through aggressive treatment to eliminate the cancer. First, the vet will most likely perform surgery to remove the tumor. Injection-site sarcomas usually affect tissue surrounding the tumor, so the vet will need to remove surrounding tissue that is not actually part of the tumor. If the tumor is on your cat’s leg, it’s common for the vet to recommend amputating the entire leg instead of performing surgery to remove the mass.

After the tumor has been removed, the vet may recommend your cat go through radiation, chemotherapy, or both to reduce the chance of another tumor developing. It’s possible your vet may also recommend radiation prior to the surgery to reduce the size of the tumor. 

Radiation is performed every day for around four weeks, and your cat will be anesthetized for each treatment. Radiation is only administered to the area that has been affected by the cancer, whereas chemotherapy is administered to the entire body. Chemotherapy is usually given in three-week intervals instead of daily like radiation treatment. Your cat will probably experience nausea, fatigue, and loss of appetite as a result of the chemotherapy, but radiation side effects are minimal.

Recovery of Injection-Site Sarcoma in Cats

All types of cancer are unpredictable, so it’s hard to predict whether your cat will recover from this condition or not. However, the earlier the cancer is detected and treated, the better chance your cat has of surviving. If the cancer has already spread to other parts of your cat’s body, the outlook is not as good. Because it’s possible for the cancer to come back after it has been treated, you will need to frequently check for new growths on your cat’s body. The vet may also recommend coming in on a regular basis so he can monitor your cat’s health.

Injection-Site Sarcoma Questions and Advice from Veterinary Professionals

16 Months
Fair condition
0 found helpful
Fair condition

Has Symptoms


We have discovered a lump in between our cats shoulder blades about 3 and a half months ago. He is 1.5 years old. It appears to be where he has received his internal parasite or steroid shot ( he has asthma ) as we cannot be sure which one has caused it or even if they are the cause. The lump is around 1,5 cm under the skin and easily movable. It did not seem to grow and it does not cause any pain when touched. Our vet performed a biopsy and advised cytology turned out as fat cells and connective tissue. He said he did not see any cancerous cells and most likely it is a lipoma. Regardless, he recommended to perform surgery to remove the lump as he cannot be 100 percent sure and it is advised in veterinary literature to remove a lump persisting long. However I do not want him going through operation stress and anaesthesia risk since he has asthma as well. And he has been diagnosed with pleural effusion two times in the last year and recovered. His lungs were filled with fluid due to toxoplasmosis or another disease that my vet could not identify. Even fip was suspected but apparently it wasn't the case. He is not coughing at all since 4 months, eating drinking very energetic and healthy. He is showing no sign of sickness at all. Therefore, I wanted to get a second opinion as how we should proceed in this case.
Thank you,

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
2466 Recommendations
The location would indicate an injection site sarcoma since they are commonly more associated with vaccinations but may be caused by any injection; you should think about having the surgery done regardless of it being an injection site sarcoma or lipoma since lipomas may grow large enough to cause issues with movement. However the decision is down to you, any surgery is at your Veterinarian’s discretion if they believe it is in the patient's best interest to have the surgery and are healthy enough for the anaesthetic. If there are doubts, it may be worth having a fine needle aspirate or biopsy sample submitted to a Pathologist for a second opinion. Regards Dr Callum Turner DVM

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5 Months
Moderate condition
0 found helpful
Moderate condition

Has Symptoms

Limping swollen paw

My kitten started limping then his right rear foot swoll and he late began dragging his body. Then within 24 hours moving trying to climb on furniture and still limping . the vet said he has fractured hip bones and foot. He accused us of hurting him. What could cause this?

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
2466 Recommendations
This sounds like a traumatic injury from either physical trauma, falling from a height (wardrobe, stairs etc…), road traffic accident (car) among other traumatic injuries. The fracture(s) would need to be stabilised and Taz would need strict rest for a few weeks during recovery. Regards Dr Callum Turner DVM

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