Are Tumors/Cancer Painful to Rats?

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There is a good chance that your rat may suffer from a tumor at some point in its life. This can be quite a scary thought. If only our rats could tell us when they are experiencing pain and where. Fortunately, there are a few things that we can look out for that might tell us that your rat’s lump is painful.

Certain types of cancers are known to be extremely painful. An example of this is osteosarcoma (bone cancer) and certain types of skin lumps. However, some types of tumors have no pain associated with them and may only cause discomfort when the size is large or when it invades or puts pressure onto surrounding tissue structures.

Whether a tumor is painful or not is dependent on a multitude of factors, including the type of tumor and the location and size of the growth. Certain types of tumors are known to be extremely painful, and other types of tumors have no associated pain.

In this article, I will go over a few of the most common types of tumors in rats and discuss whether they are painful. I included common symptoms of pain and a few things you can do to help with the pain.

What must I do if My Rat has a Tumor/Cancer?

If you think that your rat might have a tumor, you need to seek veterinary attention as soon as possible. Not all lumps you find on rats are tumors or cancer. In most cases, the earlier treatment is initiated, the better the outcome for a rat with a tumor. The most common treatment is surgical excision of the lump. Feeding a diet high in antioxidants and low in calories and carbohydrates will prevent some tumors and slow the growth of certain types of cancer.

For more details and tips on caring for a rat with a tumor, look at this article.

Which Types of Lumps are Painful?

Of course, not all lumps are cancer, and many non-cancerous lumps can be painful. Abscesses, for example, are usually very painful, but cysts (benign tissue sacs fille with fluid or other biologic material) are commonly non-painful (there are a few exceptions to this). Both abscesses or cysts are not tumors but can look very similar to tumors.

Abscesses are treatable and should resolve completely. Likewise, cysts are, depending on cause and location, usually treatable.

How Do I Know Wether My Rat Is Painful?

Rats are notoriously good at hiding signs of pain. As a prey species, their survival out in the wild depends on this because showing signs of pain will make them seem more vulnerable to predators. Therefore, it is crucial to recognize the very subtle signs of pain in rats as a rat owner.

Rats experiencing pain will show changes in behavior such as reduced activity, appetite, and unusual aggression. Changes in the facial expression of rats such as slanted eyes, folded ears, and flattened cheeks with whiskers pointing away from the face (The Rat Grimace Scale Soticina et al. (2011)).

If you would like to read more on the signs of pain and what you can do to help, look at this article on the topic.

Symptoms of pain include the following:

  1. Reduced activity
  2. Reluctance or refusal to eat and drink
  3. Unusual aggression
  4. Porphyrin staining around the eyes
  5. Writhing or twitching
  6. Increase in heart rat and respiratory rate (see how to take vital signs in this article)
  7. Changes in facial expression and posture (more detail on that in this article)

Below is a handy downloadable poster on signs of pain in rats by the University of Michigan

Are Mammary Tumors Painful to Rats?

Mammary (breast tissue) tumors are the most common tumor of female rats as nearly half of females will develop a mammary tumor at some stage in their lives. Many female rats will have multiple mammary growths during their lifetime, and many male rats will also develop mammary tumors. Sterilizing female rats at an early age significantly reduces the risk of mammary tumors. It is worthwhile considering if you know that your rat comes from a genetic line where mammary tumors are prevalent.

The mammary tissue of rats is pervasive and can be found anywhere from the armpit to the groin or on either side of the genitals. However, tumors in the axilla region are probably the most common.

Mammary tumors may present as small distinct protruding nodules under the skin or large flat, immovable lumps. These lumps are usually non-painful if small but will become painful if very large or ulcerated and secondary infection of the exposed tissue is present.

Are Fibromas and Fibrosarcomas Painful To Rats?

Fibromas are another common benign tumor in rats and usually occur on the back or sides. Depending on the location and size, these tumors can usually easily be surgically removed by your vet. In addition, fibromas are generally not painful.

Fibrosarcomas are malignant tumors of similar cellular origin as fibromas and tend to occur on the legs or sides. Because fibrosarcomas are malignant, they tend to grow rapidly but are usually slow to metastasize (spread to other parts of the body). Surgical removal of these tumors is usually more complicated due to local tissue invasion and if located on the legs.

Fibrosarcomas are mild to moderately painful. This is extrapolated from human data on this type of tumor (Khasabova et al., 2007).

Are Pituatary Tumors Painful to Rats?

My educated guess would be that, yes, pituitary tumors are painful. I elaborate on this in the following paragraphs, but rat parents and their vet need to monitor quality of life in these guys closely.

Even though this tumor is usually benign, its effects can be devastating – primarily due to its location near the base of the brain. This is the third most common cause of death of female rats, and early sterilization of female rats reduces the incidence from 20% down to 4%. The incidence of this tumor in male rats is around 7%.

Symptoms usually include slow-onset incoordination, paralysis, and walking in circles or a head tilt. In addition, some rats show strange behavior such as hyperactivity, depression, or becoming uncharacteristically cuddly. Finally, the slow onset of subtle symptoms may progress to a complete inability to use the front and hind limbs in many cases. These rats will eventually need to be hand-fed until they cannot swallow. At this point, it is best to euthanize humanely.

This tumor can have sudden onset of symptoms and be potentially fatal in rare cases. The symptoms include sudden paralysis, seizure, and death in these sudden onset cases. This is usually a result of abrupt bleeding of the large number of vessels these tumors tend to have. In a few cases of sudden tumor bleeding, the symptoms will regress if the bleeding is minor and the clot has resolved.

It is challenging to evaluate pain in a rat with neurological symptoms such as those listed above. Still, we can safely extrapolate from data on humans with pituitary tumors that headaches are a common symptom- even before any other symptoms become evident.

The treatment of pituitary tumors includes anti-inflammatory pain medication, which has been shown to slow the progression of symptoms and improve the prognosis. However, it will not shrink the tumor or prevent further growth of the tumor. The reported effect of using anti-inflammatory pain medication is simply to retard further tumor expansion.

Are Squamous Cell Carcinomas Painful to Rats?

This is a malignant skin tumor commonly found on the face and around the eyes. Secondary infection is common with this type of tumor, meaning that the affected tissue has a bacterial infection. Pain is associated with this tumor primarily because of the inflammation due to the secondary infection.

These tumors often appear like wounds that do not heal and may grow larger over time. This type of tumor is more common in non-pigmented areas (white/pink) on rats.

Are Lipomas Painful to Rats?

These are benign growths of fatty tissue, which are usually slow-growing and non-painful. These tumors are typically found under the skin anywhere on the body. Removal generally is curative, and preventing obesity will reduce the occurrence.

When is a Tumor too large and too Painful?

It is generally accepted by animal welfare guidelines that tumors start affecting welfare if they exceed 2.8 centimeters or 1.1 inches in rats. However, this is only a rough guideline and each rat should be evaluated individually for signs of discomfort or reduced quality of life.

If surgical removal is a viable option for your rat, go for it! Yes, surgery has associated risks, and recovery isn’t always easy. Still, even by simply reducing the mass size by surgical debulking, you can significantly increase your rat’s quality of life and at least buy them some more time. So again, I encourage you to talk to your vet about the treatment options for your rat.

You can read more on caring for a rat with a tumor/cancer in this article.

What Can I do to Keep my Rat Comfortable?

I go into a lot more detail on how you can keep a painful rat comfortable in this article, and you can find more tips on caring for a frail pet rat in this article. However, here are a few things that may help in the meantime:

1. Provide A Warm, Comfortable and Quiet Environment

Reduce the necessity to move around by providing your rat with easy access to water bowls and easy-to-eat food they enjoy. Food options for ill rats can include banana slices, baby puree, yogurt, or anything that does not require a lot of chewing or them holding it.

Provide soft absorbable bedding. Be ready with a change of clean bedding if they do soil their bedding due to reluctance to move.

The ideal room temperature for rats is around 70-75°F (20 – 25°C). Therefore, reducing any temperature challenge will help keep them comfortable.

2. Keep Them Calm

Knowing what causes stress to your rats and what you can do to alleviate stress will aid in keeping them as comfortable as possible when they are experiencing pain. In the article I wrote on this topic, you can read more in-depth about what may cause stress in pet rats, the symptoms of stress, and what you can do to alleviate stress.

In addition to a comfortable environment, calming products such as Rescue Remedy or Pet Remedy, you can use music and low light to help keep your rat calm. If you would like to read more about these topics, have a look at this article looking at the research on the benefits music has on rats and this article on how light affects rats.

To help keep your rat calm, avoid bright light and loud noises. Instead, please keep them in a quiet, dimly lit room and consider playing soft classical music. I discuss these topics in-depth in the two articles linked above.

When is it time?

Evaluating the quality of life is one of the ways we determine whether euthanasia is a kind option. We can judge whether a rat has a good quality of life by looking at the amount of time they spend doing things that rats enjoy doing. So if your rat still boggles when you offer them their favorite treat or still enjoys spending time outside of the cage or following you around, they may be doing just fine.

But if you find that your rat spends the whole day sleeping, constantly has urine scalding or signs of pain, and does not eat unless you place the food right in front of their nose, I would encourage you to talk to your vet.

I am a huge advocate for preventing or ending suffering. If you think that your rat may be near its end (and owners often have a good sense of when this is – trust yourself!), having them humanely euthanized by your vet may be the kindest thing you can do for your rat in such a situation—Euthanasia, when done correctly and by a veterinarian, is painless.

At the very least, let your vet have a look and help you make the decision. Sometimes our judgment becomes clouded with emotion when our own pets are having a difficult time. Having a trusted vet by your side in situations like these will help you to make a decision in the best interest of your beloved rat.

References

Dr. Annerien de Villiers

Dr. Annerien de Villiers graduated as a veterinarian from the University of Pretoria in 2018. She has since worked full-time in clinical practice tending to all kinds of companion animals in general practice. Serving the human-animal bond with care and compassion and making accurate information accessible to pet owners is at the heart of her driving force as a veterinarian.

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