A Lump In Your Cat’s Belly Is Not Always Cancer

Updated July 2, 2022

I want to share with you a very sobering paper that should make us think harder anytime we feel a lump inside a cat’s belly.

Note that this article is not about lumps on the skin of cats. Those need a checkup at the vet to know what they are.

Five cats were presented to a veterinary teaching hospital with abdominal masses that could be felt during a routine exam. They all had the classic signs of intestinal obstruction: vomiting, listlessness and not eating.

The two eldest cats died. One, because her owner thought it was cancer and had her put down. The other, due to a delay in treatment, most likely due to a similarly fatalistic attitude.

The diagnosis in these five cases was a hairball. A thoroughly treatable problem.

Types Of Stomach Lumps In Cats

Part of the problem here is a lack of good quality information. I can find no research paper which looks at how common different lumps of cats are. So this list is based on my experience alone.


There are sporadic reports in the literature of hairballs causing gastrointestinal obstructions, and I have seen them too. Risk factors might include:

  • A long coat
  • Skin and coat problems
  • Poor health for another reason

It’s worth noting that the cat who was euthanased had none of these risk factors. And the big danger with a hairball is that it feels exactly the same as a tumour.

Visit this page to read about hairball treatment and prevention, but in only a few minutes you’ll know how to recognise one.

Feline Infectious Peritonitis

You can read about FIP in more detail here, but one of its forms causes abdominal masses or tummy lumps. Clues that lumps in the belly might be caused by this dry form of FIP are:

  • a young cat
  • a persistent fever
  • a longer course of illness

Once again, these are only generalisations. I have seen FIP in older cats with no fever too.

Followers of this blog will know that there have been recent and exciting changes to how we treat FIP. What was once a death sentence is now survivable for the majority of cats. All the more reason to get that diagnosis.


Lymphoma is a tumour of one of the cells of the immune system. This is probably the diagnosis we fear the most, because it’s mostly a death sentence. Attempts at treatment are often very disappointing.

It’s true that abdominal lymphoma is one of the most common cancers of cats but there’s no way you can be certain just by feeling it. And I only see a few cases a year, much less than I see FIP.

Other Abdominal Masses

Of course, the abdomen is a complex place, and so there are many other less likely causes of lumps in the belly. Here are just some:

  • Tumours arising from any of the organs or tissues
  • Foreign bodies like surgical swabs, grass seeds or swallowed string
  • Enlarged kidneys from ureteral blockage secondary to stones

Diagnosis Of Abdominal Masses

There’s one test that should be able to distinguish between all these causes: ultrasound. It’s neither difficult, invasive nor terribly expensive.

cat lymphoma ultrasound
  • A hairball will show itself as a mass inside the stomach or intestine containing large amounts of gas
  • FIP mostly causes many irregular masses in the mesentery between the intestines
  • Lymphoma can be the same, or a single larger mass like pictured, and easily diagnosed by ultrasound-guided needle biopsy
  • Enlarged kidneys, abscesses or other tumours are usually just as obvious

Some vets may prefer to do CT, MRI or even exploratory surgery. All of these are good, and a whole lot better than not trying at all.

Going back to that paper at the start, it’s important to look at who published it. Although they don’t say so, most or all of those cats were probably referred from other vets. Whenever I read this I always think: “great, but referral is only the tip of the iceberg”.

Many more cats could have had similar experiences at private veterinarians and we would never know. But against this very negative outlook is a very positive one.

20 years have passed since this study was published. In that time ultrasound has gone from a referral procedure to one that nearly every vet practice can do well.

Therefore, despite my warnings, I’m confident that we aren’t euthanasing many cats with hairballs any more. But it requires a positive attitude, too!

Have something to add? Comments (if open) will appear within 24 hours.
By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. Meet his team here.

The paper I mentioned was:
Barrs, V. R., Beatty, J. A., Tisdall, P. L. C., Hunt, G. B., Gunew, M., Nicoll, R. G., & Malik, R. (1999). Intestinal obstruction by trichobezoars in five cats. Journal of Feline Medicine and Surgery, 1(4), 199-207

6 Replies to “A Lump In Your Cat’s Belly Is Not Always Cancer”

  1. My cat (female) is almost 8 months old and we just found a lump on her stomach near one of her nipples. We’re trying to find a vet who will see her as my husband is a travel nurse so we’re currently living away from her normal vet for 3 months. She’s been eating less wet food for a week or two now which we thought was strange and she’d attitude is changing a little bit, I hesitate to say lethargic because she’s still very playful and wants attention at points throughout the day but perhaps less than normal. She’s skinny compared to our other cat, but her previous vet never said she was underweight so we haven’t been too concerned until she started eating less.

    1. Hi Emma. There’s not much to go on here but I would guess that it’s going to be an infection.

  2. My cat Ellies back legs stopped working and she was lethargic. She had a temp of 205 and presented anemic. Her legs were warm but gave her no support. She cried if picked up by belly. I took her to emergency vet and he said he felt a mass. Ustrasound was not available the radiologist was gone. He talked me into putting her down and now I am heartbroken that I should of taken her somewhere else. Not knowing what was causing this is killing me. She was 15

    1. Hi Linda. At her age, the lump was very likely to be a tumour. While an ultrasound would have been ideal, euthanasia was not inappropriate.

  3. My cat died a few weeks ago after it got to some salmon I foolishly let out. He ate too much, there was a hard ball in his stomach and was unable to pass the food and passed away a few days later. How can I save a cat in the future? How would a vet treat this?

    1. Hi. I hope you can see from the article that if no diagnostic imaging was performed then I doubt that the salmon had anything to do with the cause of death.

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