Feline Vaccine-Associated Sarcoma

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Article Written by Dr. Daniel A. Degner, Board-certified Veterinary Surgeon (DACVS)

Animal Surgical Center of Michigan

5045 Miller Road

Flint, MI 48507


Phone: 810-671-0088

Key Points

Vaccination can cause the formation of a highly invasive tumor

Treatment involves a combination of radical surgery, radiation therapy and chemotherapy

Prognosis is fair with recurrence of the tumor expected with time in many patients


In 1979, an outbreak of rabies in wildlife was noted. At that time, there were very few cats that were vaccinated for rabies and the fear that domestic cats would contract rabies from wildlife and be a threat to humans. The need for vaccinations had become evident. In 1985, two aluminum adjuvant vaccines, feline leukemia and rabies were developed and subsequently used clinically. A few years later, veterinarians were reporting vaccination reactions. Some of these were biopsied and found to have inflammation with a core of brown unidentifiable material. It was suspected that the material was the aluminum adjuvant, the vaccine itself or a combination thereof. In 1991, Hendrick reported the first vaccine-associated sarcoma. Others have reported the development of a sarcoma at the site of the excised vaccination reaction. Interestingly, some cats developed multiple sarcomas located at each vaccination injection site. Epidemiologic associations first were made with feline leukemia and rabies vaccination and later with feline panleukopenia and feline rhinotracheitis vaccines.


Vaccine Reactions

Cats can develop a lump (mass) at the site of a vaccination injection. Usually the mass will resolve spontaneously and does not form into a cancer. In general 1:10,000 vaccinated cats will develop cancer due to the vaccination. If a mass has been present for more than 3 months, if it is greater than 2 cm in size, or if it has increased in size one month after the vaccination was administered, then a biopsy of the mass should be performed. If a cat has had a tumor removed due to vaccinations and later is vaccinated, early tumor recurrence is likely. Vaccine-associated sarcomas Cancer can develop in the layer of connective tissue between the skin and muscle. These tumors have microscopic cells that extend like roots deeply into surrounding tissues. For this reason, recurrence of the tumor following tumor surgical removal is very common. Although only 3 to 5% of the patients will have spread of the tumor to the lungs, skin, subcutaneous tissues, region lymph nodes, chest, liver and pelvis at the time of initial diagnosis, with time the spread rate increases to 24%.



Signs and diagnosis

The typical sign of a vaccine-associated sarcoma is a mass (lump) at the site of a vaccine injection site. The most common locations for vaccination-associated masses include the back, shoulder blades or on a limb. The mass commonly is firm, nonpainful and frequently is attached to the skin or underlying muscles. Most patients do not feel ill when the lump is first found. If left untreated these masses can become ulcerated and infected. With time they can spread to lungs and other parts of the body and cause breathing difficulty, anorexia and weight loss. The diagnosis of a vaccine-associated sarcoma necessitates a biopsy. Additional tests done prior to surgery may include a complete blood count, blood chemistry profile, Feline immunodeficiency virus infection test, Feline leukemia virus test, and urinalysis to check internal organ health. Chest x-rays and are used to rule out visible spread of the cancer. A CT scan (see left) helps the surgeon develop a plan to surgically remove the tumor.


The day of surgery

Our anesthesia and surgical team will prescribe a pain management program, both during and after surgery that will keep your companion comfortable. This will include a combination of general anesthesia, injectable analgesics, local anesthetics, oral analgesics and anti-inflammatory medication.



Surgery is an essential treatment for vaccine-associated sarcomas. For the best outcome, sarcomas should never be shelled out of their bed. The tumor and a large zone (2 to 5 cm) of surrounding skin, fat and muscle should be removed. If the tumor is located on a limb, amputation is essential for a good outcome.

Chemotherapy may be recommended and is administered every three weeks via intravenous injection by our oncologist for a total of four to five treatments. The treatments are typically done on an outpatient basis and may take a total of 90 minutes to complete each visit. Unlike humans, most cats do not lose their hair and usually have only mild side effects from the medication such as transient loss of appetite and vomiting.

Radiation therapy has been shown to improve the survival of patients that have surgery may be used to shrink an inoperable tumor or used to kill residual cells that may be present. Radiation is administered daily (Monday through Friday) until 18 to 21 treatments have been completed.



After surgery, a prescribed pain reliever should be given to minimize discomfort. It’s also extremely important to limit your companion’s activity and exercise level for three weeks after surgery. The incision should be checked daily for signs of infection. Two weeks after surgery, the surgeon will monitor the healing process and our oncologist will initiate chemotherapy or radiation therapy if indicated by the biopsy report.



With “dirty” surgical margins and no additional therapy, the median disease free interval (time until tumor recurred) was reported to be 2 to 6 months. With “clean” surgical resection of the tumor (radical surgery) and no additional treatment, median disease free interval was 276 days and median survival time was 576 days. With “clean” surgical margins and radiation therapy, the disease free interval was 1year with a median survival time of 2 years. In another study, preoperative radiation followed by surgery resulted in a disease free interval of 986 days with “clean” excision of the tumor versus 292 days with incomplete excision. A more recent report indicated that surgery and radiation with “clean” surgical margins had a disease free interval of 37 months and median survival time of 43 months. Short-term complications following surgery are uncommon and may include temporary dehiscence (opening) of the incision and infection. Tumor recurrence and spread of cancer are other complications. Side effects of radiation may include skin burns, poor healing of the incision, dermatitis, and regrowth of hair coat that is a different color (grey or white).



  1. Hershey AE, et al. Prognosis for presumed feline vaccine-associated sarcoma after excision: 61 cases (1986-1996).J Am Vet Med Assoc 2000; 24:20-3
  2. Cronin K et al. Radiation therapy and surgery for fibrosarcoma in 33 cats. Vet Radiol Ultrasound 1998;38:51-6
  3. Davidson EB et al. Surgical excision of soft tissue fibrosarcomas in cats. Vet Surg 1997;26:265-9
  4. Poirier VJ et al. Liposome-encapsulated doxorubicin (Doxil) and doxorubicin in the treatment of vaccine-associated sarcoma in cats J Vet Intern Med. 2002 Nov-Dec;16(6):726-31
  5. Kobayashi T et al. Preoperative radiothereapy for vaccine associated sarcomas in 92 cats. Vet Radiol Ultrasound 2002 Sept-Oct:43(5):473-9
  6. Eckstein C et al. A retrospective analysis of radiation therapy for the treatment of feline vaccine-associated sarcoma.Vet Comp Oncol. 2009 Mar;7(1):54-68.

Frequently Asked Questions After Surgery

When should my dog have the first bowel movement after surgery?

  • Many dogs will not have a bowel movement for the first 4 to 5 days after surgery
  • Reasons that a dog will not have regular bowel movements after surgery include:
    • The dog has been fasted prior to surgery
    • Dogs do not eat well during the hospital stay
    • They frequently do not eat well when they go home
    • They are fed highly digestible food that produces little stool
    • Pain medication that contain narcotics (such as morphine, fentanyl patches, and tramadol) can be constipating
  • If a pet does not have a bowel movement on the 5th day of being home, a stool softener such as metamucil can be fed
    • Dose of metamucil is 1 tsp per 25 Kg mixed in with each meal (canned dog food); feed immediately after mixing, as the metamucil will gel the food and may make it less palatable

My pet had surgery and will not eat.  What can be done?

  • Dogs
    • Most pets will not eat their regular dog food after surgery, especially if it is kibble.
    • Offer a cooked diet having a 1:1 ratio of a protein source and carbohydrate source.  The protein source can be any meat (example: chicken breast, turkey breast, lean hamburger) that is low in fat and should be cooked (drain off all fat after the meat has been cooked).   The carbohydrate can be pasta, potato or white rice.
    • Try canned dog food; to enhance the flavor sprinkle a very small amount of garlic powder or chicken or beef broth (Chicken-in-a- MugTM or Beef-in-a-MugTM products)
    • Try Gerber strained meats for babies such as the chicken, beef, turkey, or veal
    • Try Hill's A/D diet available at most veterinary hospitals
    • Hand feeding: place a small amount of food in the mouth so that your dog gets the flavor
    • Warm the food slightly in a microwave, as the food will be more aromatic; stir the food before feeding and test the temperature on the bottom side of your wrist; it should only be luke warm.
    • Remember that most pets will not eat the first day or two after they get home from surgery
  • Cats
    • Offer smelly foods that contain fish such as tuna or smelly cat foods
    • Try Gerber strained meats for babies such as the chicken, beef, turkey or veal
    • Hand feeding:  with your finger place a small amount of food on the roof of your cat's mouth; use a syringe to get soft food into the mouth
    • Warm the food slightly in a microwave as the food will be more aromatic; remember to stir the food before feeding and test the temperature; it should be only luke-warm
    • Some cats will only eat dry food, try kibble if your cat normally has been fed that food
    • Petting and stroking your cat frequently will help to stimulate appetite
    • Remember that most pets will not eat the first day or two after they get home from surgery
    • Appetite stimulants such as cyproheptadine may be helpful
    • If your cat refuses to eat anything for 7 days a stomach tube or nasogastric tube should be placed to provide nutrition so that a serious liver problem (hepatic lipidosis) does not develop

My pet is vomiting.  What can be done?

  • The first thing for you to discern is whether your pet is vomiting or regurgitating.  Both will result in fluid or food being brought up.  Vomiting always will have heaving or retching of the abdomen prior to expulsion of the vomitus.  Regurgitation is not associated with heaving and the pet usually just opens the mouth and fluid or food will be expelled.  Usually the regurgited material will be clear or brown colored fluid. 
  • Next is to identify the cause of the vomiting or regurgitation.
  • Causes and treatment of vomiting after surgery
    • When some pets return home after a stay in the hospital they may drink excessive amounts of water at one time and then vomit; if this appears to be the case, the water should be limited to frequent smaller amounts.
    • Medications such as antibiotics, narcotics or nonsteroidal anti-inflammatory medication commonly cause vomiting after surgery.  In order to see which medication is causing the problem, the administration of each drug should be separated 2 hours apart.  Usually the pet will vomit or appear nauseated (drooling and sick look) within 1 hour of administration of the medication that they are sensitive to.  The antibiotic in some cases may be changed to a different one, or may be discontinued. 
    • Stomach upset from anesthesia is a potential cause of vomiting and will pass within a couple of days. 
    • An uncommon cause of vomiting after surgery is internal organ failure.  Blood testing will confirm this problem. For this reason vomiting should not be ignored if it persists for more than 24 hours.
    • If your pet had surgery of the bowels or stomach, vomiting is always a concern, as it may indicate that infection of the abdominal cavity, called peritonitis, is present.  Do not ignore this sign.
    • Symptomatic treatment of vomiting involves withholding food for 12 to 24 hours, then introducing small amounts of bland food such as rice and lean cooked hamburger, if your pet does not vomit after that then gradually wean him/her back onto the regular diet after 3 days.  In order to decrease the acidity of the stomach, Pepcid AC 0.5 mg/kg can be given by mouth twice daily for 5 days.  Metoclopramide and Cerenia are good anti-vomiting medications for dogs and cats.  You should always consult a veterinary healthcare professional before administering medication.
  • Causes and treatment of regurgitation after surgery
    • The most common cause of regurgitation is reflux of acid from the stomach into the esophagus while your pet is under anesthesia.  Acidic fluid from the stomach can cause a chemical burn of the esophagus and result in a bad case of heart burn, called esophagitis.  This results in poor motility of the esophagus, therefore water and food will accumulate in this structure.  In most cases, esphagitis is self-eliminating and will resolve within two or three days. 
    • If the esophagitis is severe the esophagus may develop one or more strictures.  A stricture is a narrowing or stenosis of the esophagus and does not allow passage of food down the esophagus, in regurgitation that lasts longer than one week.  This problem should be brought to the attention of your pet's doctor within the first two weeks so that it can be treated by ballooning the stricture (minimally invasive procedure, as it is done with the aide of an endoscope).  If an esophageal stricture is chronic surgery is needed.
    • Symptomatic treatment of regurgitation caused by esophagitis includes feeding bland food, and administering a coating agent (sucralfate) and an acid blocker (omeprazole or other).  Consult a veterinary health care professional if the regurgitation continues for more than a couple of days.

How do I know that my dog is in pain following surgery?

  • Signs of pain include
    • crying
    • biting if you get near the surgical site
    • grimacing (lips are pulled back and the the dog looks anxious)
    • tragic facial expression
    • panting
    • restlessness and unable to sleep; pacing
    • if abdominal surgery was done the pet will not lie down on the incision, or will continually sit up in spite of appearing very tired
    • the worst pain will be for the first 2 to 3 days after surgery

What can I do to control my dog's pain?

  • Narcotic medications that control pain: tramadol, butorphanol, Duragesic (fentanyl patch)
  • Anti-inflammatories used to control pain: Deramaxx, Rimadyl, Previcox, or Etogesic
  • If an orthopedic surgery has been done cold packing the surgical site may be helpful
    • A cold pack may be a pack of frozen peas, crushed ice in a Ziploc bag, or a cold gel pack; place a thin barrier between the skin and the cold pack.  An alternative to a cold pack is to freeze water in a styrofoam cup; after frozen cut the bottom of the styrofoam cup out. Cool the surgical site around the incision by rubbing the exposed ice directly on the skin in a circular pattern.  Cooling the surgical site helps to numb the area.

How do I know that my cat is in pain following surgery?

  • Pain is more difficult to assess in cats versus dogs, as signs can be more subtle and they usually do not vocalize when in pain
  • Signs of pain in a cat include the following:
    • biting if you get near the surgical site
    • growling or deep cry
    • not wanting to eat
    • hiding and not wanting to be near owner (remember that this could also be caused by the cat just being upset about leaving home and coming back)

What can be done for pain at home for my cat?

  • Pain medication such as buprenorphine or a Duragesic (fentanyl) patch
  • Tylenol will kill a cat as they lack abundant glutathione enzyme in the liver
  • Anti-inflammatories can be used, but the dose is much less than dogs

Is it okay for my pet to lick the incision?

  • If a dog licks the incision, the healing process may be delayed.
  • Licking can remove stitches and cause the incision to open
  • Licking can become a severe habit that is difficult to break
  • Licking can cause infection as the mouth has many bacteria
  • Dogs will frequently lick the incision when the owner is not watching such as at night time; if the skin looks red or excoriated the most common cause is from licking.
  • To stop your pet from licking the following can be tried:
    • Elizabethan collar can be placed on the neck; this will not help stop your pet from scratching at the region
    • Cervical collar (bite not collar) is a less awkward device and can be effective at stopping a pet from licking the surgical site
    • A tee shirt can be used to cover an incision on the chest or front part of the abdomen; gather the waist of the shirt up over the dog's back and wrap an elastic band around this part of the shirt.
    • A bandage or sock can be used to cover an incision on a limb; fasten the top of the sock to the dog's limb with tape.
    • Bitter apple can be applied around the incision; many dogs will continue to lick  after application of this topical
    • Bitter Apple and Liquid HeetTM (obtain this from a drugstore...it is used for sore muscles) mixed in a 2:1 ratio can be applied around the skin incision
    • Antipsychotic medication in some cases is needed

Board-certification by the American College of Veterinary Surgeons

What does it mean?

  • Four years of advanced training in surgery beyond the Doctor of Veterinary Medicine Degree

  • Experience in the development of new surgical treatments

  • Rigorous examination by the American College of Veterinary Surgeons to ensure competency in advanced surgical techniques

  • Assurance that a veterinarian is a surgical specialist

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