Breast Cancer in Cats – Signs and Prevention

Did you know breast cancer in cats is the third most common type of feline cancer?

There are three common cancers in cats. These are, in order:

1. Blood cancers, such a leukaemia
2. Skin cancers, such as squamous cell carcinoma or malignant melanoma
3. Breast cancer.

It is perhaps, a surprising statistic that breast cancer is as high on this list as it is. Mammary tumours in cats is not something that pops readily to mind when worrying about our cats’ health . . . but it does happen.

Whilst mammary cancer is more common in dogs (it can affect one-in-four entire female dogs!) – when it does occur in cats it’s usually a more aggressive form of cancer and has a higher malignancy rate.

Like all cancer diagnoses, if it’s caught early and treated quickly there is a much higher rate of survival.

Preventing Breast Cancer in Cats

But don’t panic. Spaying your cat before six months of age is a preventative for mammary cancer. It’s therefore important that you know the facts about breast cancer in cats so you can make informed decisions about early age neutering. As it turns out, preventing pregnancy isn’t the only major benefit of spaying.

But before we get ahead of ourselves, let’s look at the facts concerning breast cancer in cats.

Breast Cancer in Cats: Facts and Statistics

• Breast cancer represents 11% of all feline mammary tumours regardless of sex
• Senior female cats aged 10-14 years are most at risk of breast cancer
• 85-95% of breast cancer in cats is malignant and potentially life-threatening
• An entire cat is seven times more likely to develop breast cancer than a spayed one
• Spaying before the first oestrous (season) prevents breast cancer.

Breast cancer is a hormonally driven condition. The more exposure the mammary tissue has to female hormones, the greater the risk of it undergoing cancerous change. For example, spaying your cat:

• Before 6 months of age means a 91% reduction in risk
• Within 7 – 12 months of age means an 86% reduction in risk
• At 13 – 24 months offers an 11% reduction in risk
• After 24 months of age offers no protective benefit.

What Causes Mammary Tumours in Cats?

Role of Hormones

The mammary glands are rich in receptors for various female hormones. It is these hormones that prepare the breasts to produce milk to nurture a new litter of kittens. However, they also have a downside.

Repeated floods of hormones, which the cat experiences every time she comes into heat, can cause problems. These are known as ‘malignant transformation’. In other words, repeated hormonal stimulation can change the way tissue behaves and cause it to become cancerous.

This is why there’s such as strong link between whether a female cat is spayed or not. Bear in mind that a female can come into heat every three weeks or so, and that’s a lot of hormones sloshing around her body. Removing her ovaries (spaying) means taking away the source of those over-stimulating hormones which can cause malignant transformation.

Synthetic Progestogen Drugs

Synthetic progestogen drugs which replicate the naturally-occurring female hormones (such as Ovarid) have been scientifically linked with an increase in mammary cancers. Once regularly prescribed for a range of cat health and behavioural issues, from skin allergies to territory marking, they have now seriously fallen out of favour. Giving extra hormones in tablet form primed up the mammary tissue, even in spayed cats. Prescribing synthetic progestogen is now considered the equivalent of feeding candy to a diabetic.

Breed Types at Greater Risk

Siamese cats, Oriental breeds and domestic short hairs are most often affected by breast cancer, according to the ACVS.

Signs of Breast Cancer in Cats

So what should you be looking out for?

The answer is simple: Lumps in the mammary area.

This is where is pays to give your cat regular belly rubs. Familiarise yourself with your cat’s body so you know what’s normal and what’s not – start by getting your cat used to being touched and stroked during petting and grooming sessions. This will make it much easier for you to feel for any small lumps or bumps in the mammary area.

Nipples are Normal

“But I didn’t know cats had nipples.”

Our vet says she’s lost count of the number of times a concerned owner has brought their cat in to have a tick removed. . . only to find it’s a nipple. Boy cats have nipples too, so it’s best to find them now and recognise what’s normal. Interestingly, male cats can develop breast cancer, although this is rare.

If in doubt as to whether a lump is a nipple or not, compare it with the other side of the body. The former usually come in pairs, so if there’s a matching ‘pimple’ on the other side, the chances are its normal. There’s some variation between individuals, but most cats have eight nipples (four on either side, arranged in pairs).

Cat owners need to be alert for bumps, lump, ulcers, and thickening around the nipple or the tissue between nipples (which are all part of the mammary gland network). Like breast tumours in humans, the first sign of a mammary tumour in cats is a small but firm, moveable bump under the skin. If you find anything unusual, anything at all, see your vet.

Types of Mammary Tumours in Cats

There are two basic types of mammary cancer in cats. Approximately 85% of feline mammary tumours are malignant adenocarcinomas, aggressive tumours that often metastasize to the surrounding lymph nodes and lungs. The remaining 15% include duct papillomas, sarcomas, and adenomas.

Breast cancer in cats is often aggressive, so the best outcomes occur when cats are seen early and prompt veterinary action is taken.

Treatment of Breast Cancer in Cats

The number one option for treating breast cancer in cats is surgery.

It is a sad fact that the aggressive nature of this condition means the “wait and see” approach is not a great idea. Instead, surgical removal of the lump is often best. Your vet may even suggest what may seem like unnecessarily big surgery at the time, a mastectomy.

There is evidence that removing all the breast tissue along the side with the lump, improves the long term outcome. This is because cancer cells can seed-off early on in this disease, and there may already be microscopic spread even if a solitary lump is present at the time.

Indeed, the gold standard is to go further than this. Taking chest x-rays and harvesting a small sample of cells from the draining lymph node, help the vet ‘stage’ the cancer. This simply means they are able to work out if the entire lump has now gone, or whether the cancer has already spread further.

In the unfortunate event that the cancer has spread, then chemotherapy may be considered. However, the response to the drugs can be disappointing, so all in all, radical surgery straight out of the blocks is still the cat’s best option.

You Can Reduce your Kitten’s Risk!

Remember, there’s something you can do which reduces the risks right away. Ensure your female cat is spayed before six months of age. Mammary tumours and breast cancer then becomes one less thing to worry about.

Even if you have an indoor cat, there are sound health reasons for getting her desexed as this article explains.