Tumors in Rats

White rat on black background
Rats are prone to developing tumors

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Rats are far more lovable than many people think which makes them great pets for those with limited space. Rats are incredibly smart, very friendly, and develop such unique personalities. Unfortunately, rats also have relatively short lifespans which is often because they tend to develop tumors. Because of how common it is for rats to develop tumors, it is important for rat owners to know more about these potentially life-threatening growths.

What Are Tumors in Rats?

A tumor refers to a mass or growth on a rat. Tumors can range from being less worrisome, benign cysts or lipomas to troublesome malignant, cancerous tumors. Some growths aren't cause for concern but most tumors in rats get so large that they need to be removed due to the small stature of the animal. Tumors can develop on the skin of a rat where they are visible or internally where they may go unnoticed for some time. Some of the most common types of tumors in rats include:

  • Mammary tumors
  • Lipomas
  • Cysts
  • Cancerous tumors
  • Brain tumors

Signs of Tumors in Rats

Signs a Rat Has a Tumor

  • Difficulty walking or climbing
  • Pain
  • Weight gain
  • Visible lump
  • Increased appetite
  • Bulging eyes
  • Misshapen head
  • Ataxia

Different types of tumors may be more obvious than others. Some tumors grow quickly and are easy to spot, while others are hidden internally and may go unnoticed until your rat starts having trouble getting around or seem painful when picked up.

Depending on the location, your rat's movement may be impaired which can lead to lethargy, poor appetite, and weight gain from a growing tumor. But some tumors may actually spike an increased appetite in your pet rat. However, a rat that eats a lot of food but gains little to no weight may be experiencing a nutritional offset where the intake of nutrients is directed toward the growth of the tumor.

Brain tumors usually cause neurological symptoms as well as bulging eyes and a misshapen head due to tumor expansion. Rats with brain tumors may be ataxic and have problems getting around or appear wobbly.

Causes of Tumors in Rats

Depending on the type of tumor, the causes can vary.

  • Mammary tumors - These are fast-growing and hormone-dependent tumors, responding to both estrogen and prolactin and are most often seen in female rats that are not spayed.
  • Lipomas - Also known as fatty tumors, lipomas are pockets of fat tissue that can surface on any part of a rat's body. No cause other than genetics has been linked to their growth and large growths can impede a pet rat's movement.
  • Cysts - Male rats are the most prone to developing cysts. Cysts are not actually considered tumors (unless it is a cystadenoma) and are often found on a male rat's back near its sebaceous glands. Cysts can pop up from a simple skin infection or ingrown hair. They are usually quite firm and do not grow as large as a lipoma or mammary tumor.
  • Cancerous tumors - Unfortunately no one knows what causes all types of cancerous tumors but they are common in rats. Cancerous tumors can be found on various parts of the body and may be due to poor breeding or exposure to carcinogens.
  • Brain tumors - Both benign and malignant brain tumors can be caused either by the presence of cancer or by an abnormality in the pituitary gland. They are sometimes also affected by the increased consumption of high-calorie foods.

Treatment of Tumors in Rats

Mammary tumors and large lipomas are often surgically removed, especially if they are suspected to be cancerous or causing ambulation issues in your rat. Some growths are difficult to completely remove and regrowth is common though.

Cysts are usually lanced or popped by your vet, causing the thick secretion (or infection) to ooze out. Cysts need to be watched for infection and can regrow, leading to later surgical removal.

Brain and certain types of cancerous tumors are inoperable in rats unfortunately. Yet, some types of cancer can be treated with drugs like Tamoxifen (for estrogen-sensitive cancers) and supplements like turmeric and shark cartilage are reported to stunt a tumor's growth. Rats with severe health issues, however, should be euthanized once their quality of life is compromised.

How to Prevent Tumors in Rats

Feeding a rat a nutritious, low-fat diet may help prevent cancerous tumors in some rats and several studies also show a decrease in mammary tumor formation in rats fed a diet high in miso, a soybean product. Spaying or neutering your pet rat may help reduce the likelihood of it developing cancerous breast tumors.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.
Article Sources
The Spruce Pets uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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