The #1 Rat Health Problem: Tumors

on April 21, 2010
Posted in News

Rats can make wonderful pets: they are smart, easy to train and can be extremely affectionate. They need daily love and attention, but don’t require  walks around the block or large areas to explore. Relatively speaking, they are low maintenance pets.

But rats are predisposed to tumor growth, which can cause extreme discomfort and even premature death. As a rat owner, you need to know how to prevent and manage this potentially life-threatening ailment!

Tumors In Rats: A Serious Health Issue

The most common rat tumor is the mammary tumor. While most often found in un-spayed females after the age of 1 1/2 years, and therefore hormone dependent, it can also be found in a male. This kind of tumor can be found in the pit of the arm, the abdomen, and groin.

Mammary tumors are mostly non-cancerous, but can grow to be half the body weight of the rat. This can affect the functioning of other organs, make grooming and moving around difficult, and also interfere with feeding. Ultimately, if the tumor impacts other organs it can cause internal problems – and even death.

Other tumors are also common, and again while many are benign other are cancerous.


Hormones: Mammary tumors are very common in female rats, more than in males. This is because this type of tumor is hormone dependent, based on estrogen and prolactin (hormones controlled by the pituitary gland and the hypothalamus) receptor concentrations.

Exposure to chemicals: Rats are consistently exposed to cancer-causing chemicals, in their bedding (pine and cedar contain suspected carcinogens), commercially prepared foods (preservatives), pesticides on fruit and vegetable peels etc. Because rats are small creatures, their chemical load intake is significantly higher than larger animals (think one carrot to a rat, vs one carrot to a human).


Rats are very prone to tumors as they age, and since a rat’s lifespan is so short, you can think of every 10 days as being a year. Rats age quickly! So it’s important to do almost daily body checks to determine the health status of your pet.

Start by gently holding your rat, and running your hand over its body. Feel for any lumps. If you notice any, make an appointment to see your vet.

Also take note of any symptoms that may be present.

Symptoms of Tumor Growth In Rats

  • A soft, round or flat growth that may be moveable
  • A firm, unmoveable growth
  • Impaired movement
  • Increased appetite with no weight gain – nutritional intake will be directed to tumor growth
  • Poor appetite, weight loss, and lethargy
  • Development of one or more growths

Your vet will examine your rat in much the same way. Once a lump is detected, either an x-ray or ultrasound can help determine the size and placement.

To diagnose whether a mass is cancerous or not, your vet might want to take a fine needle biopsy.

Conventional Treatment

Many vets will advise removing a tumor with surgery. Even if a tumor is non-cancerous, most can grow very quickly and cause other health problems. As stated above, a growing tumor can affect other organs, grooming, feeding, and mobility. Ultimately, if the tumor impacts other organs it can cause internal problems – and even death.

While surgery can be expensive and anesthesia can be harmful – especially for older rats at risk – rats often make a speedy recovery. Removal of a tumor can also add longevity to an ill rat’s life.

The #1 Way To Prevent Tumors In Rats

Because most tumors are hormone dependent, most vets recommend spaying and neutering your pet rat.

Aside from spaying or neutering your pet rat, the next best preventative measures include managing your rat’s diet.

A study published in 2006 suggested that diet directly influenced tumor growth in rats. Free-fed rats were shown to have a higher incidence of pancreatic, mammary, and pituitary tumors than rats fed a restricted diet of the same foods. And the type of food is extremely important.

Anti-tumor Diet

Rats thrive on a fresh fruit, veggie and grain diet. Bright orange, blue, and dark green veggies are perfect for your rat, as are ancient grains. Small servings are key, and feed once daily – preferably later in the evening, as rats are more active at night.

Foods To Avoid:

  • Anything carbonated (like soda)
  • Anything high in fat, salt or sugar
  • Iceberg lettuce
  • Overly processed food
  • Blue Cheese
  • Alcohol
  • Dairy products (except for occasional yogurt)
  • Uncooked potatoes, brussel sprouts or yams
  • Peanut butter unless it’s thinned with water or soy milk, or baked into something. Plain peanut butter is too thick and sticky, and your rat can choke on it.
  • Oranges

Best Foods For Rat:

  • Whole grains (wheat, millet, rice, quinoa etc).
  • Blueberries
  • Broccoli
  • Dark green veggies
  • Cooked yams

Your pet is your beloved companion. Unlike a dog or a cat, living with your rat won’t be a decades-long experience – so help make it as long as possible!

Recommended Reading

Rat Health Care
by Debbie Ducommun

Rats!: For Today’s Pet Owner
by Debbie Ducommun

Training Your Pet Rat
by Barbara Somerville, Gerry Bucsis

The Rat: An Owner’s Guide to a Happy, Healthy Pet
By Ginger Cardinal

Read also: Pet Parents Coping with Cancer

Our Expert

Dr. Janice Huntingford
Janice Huntingford, DVM, has been in veterinary practice for over 30 years and has founded two veterinary clinics since receiving her Doctor of Veterinary Medicine at the Ontario Veterinary College, University of Guelph. She has studied extensively in both conventional and holistic modalities. Ask Dr. Jan

Related Posts