Many of these dogs can go on to lead a normal life with the right treatment. Others cannot be saved, and treatment could do more harm than good.

Here I’m going to help you decide what to do if a vet finds a mass in your dog’s spleen.

Signs Of Spleen Tumours

There are three ways your vet might diagnose a splenic mass:

1. They might find it without any symptoms during a health check (vets routinely feel the spleen during a physical exam)
2. The mass might rupture, leading to sudden collapse or a swollen abdomen secondary to internal bleeding
3. A dog may start losing weight or become lethargic and the cause is found after investigation

The decision on whether to operate is often based on the chance of complete cure, which is only possible if the mass is benign. However, we don’t have any way to be 100% sure before surgery. All we can do is show you the odds based on your dog’s situation.

Splenic Masses: The Odds Of Malignancy

Here’s what we know:

• Overall, half to two thirds of splenic masses are malignant depending on the study (I believe it to be 50%*)
• Splenic masses found without symptoms are malignant only 30% of the time
• If a mass has bled into the abdomen, the odds of malignancy are around 70%.
• Small-breed dogs are more likely to have benign disease
• A dog with signs of weight loss or poor appetite is likely to have late stage disease

Once your vet performs some tests, we can further finesse these odds:

• Masses being found on the liver at the same time increase the chance of malignancy to at least 75% (especially if more than one)
• The smaller the mass is when it causes symptoms, the worse it is
• The presence of low blood platelets or nucleated red blood cells worsens the odds

If you have access to both blood tests and a good ultrasound examination, there is even an online tool designed to help you estimate the odds of malignancy. Find it here.

* Some studies have drawn their subjects from emergency services, which leads to a higher percentage of serious cases that in the general population

How Long Dogs Live With Splenic Tumours

The lifespan after diagnosis mainly depends on whether the mass is benign or malignant (cancerous). This is why an estimation of the odds of malignancy is so important.

• If the mass is benign, surgical removal is mostly curative and lifespan is around normal
• If the mass is malignant, survival times after surgery are typically less than 60 days

While there’s nothing wrong with a surgery that gives 1-2 months of good quality life, most people would not choose to operate if they knew, and that’s OK. These dogs are probably best kept comfortable and quiet until a humane decision is needed.

I’ve written before about how haemangiosarcoma is the disease often associated with so-called miracle cancer cures. Most of the time these cases will have had a benign lesion mistaken for a malignant one. This only goes to show how hard it is for everyone.

The reality is that you will never know with certainty before the spleen is removed, and it’s OK to base your decision on the little you have. No one should ever feel they have to operate. However, I hope I’ve given you a realistic guide for what to do if it happens to your dog.

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 information provided here is not intended to be used as a substitute for going to the vet. If your pet is unwell, please seek veterinary attention.

Some Light Reading!

Cleveland, M. J., & Casale, S. (2016). Incidence of malignancy and outcomes for dogs undergoing splenectomy for incidentally detected nonruptured splenic nodules or masses: 105 cases (2009–2013). Journal of the American Veterinary Medical Association, 248(11), 1267-1273

Eberle, N., Von Babo, V., Nolte, I., Baumgärtner, W., & Betz, D. (2012). Splenic masses in dogs. Part 1: Epidemiologic, clinical characteristics as well as histopathologic diagnosis in 249 cases (2000-2011). Tierarztliche Praxis. Ausgabe K, Kleintiere/Heimtiere, 40(4), 250-260

Mallinckrodt, M. J., & Gottfried, S. D. (2011). Mass-to-splenic volume ratio and splenic weight as a percentage of body weight in dogs with malignant and benign splenic masses: 65 cases (2007–2008). Journal of the American Veterinary Medical Association, 239(10), 1325-1327

Leyva, F. J., Loughin, C. A., Dewey, C. W., Marino, D. J., Akerman, M., & Lesser, M. L. (2018). Histopathologic characteristics of biopsies from dogs undergoing surgery with concurrent gross splenic and hepatic masses: 125 cases (2012–2016). BMC research notes, 11(1), 1-5.

O’Byrne, K., & Hosgood, G. (2019). Splenic mass diagnosis in dogs undergoing splenectomy according to breed size. Veterinary Record, 184(20), 620-620

Stewart, S. D., Ehrhart, E. J., Davies, R., & Khanna, C. (2020). Prospective observational study of dogs with splenic mass rupture suggests potentially lower risk of malignancy and more favourable perioperative outcomes. Veterinary and comparative oncology, 18(4), 811-817

Wendelburg, K. M., Price, L. L., Burgess, K. E., Lyons, J. A., Lew, F. H., & Berg, J. (2015). Survival time of dogs with splenic hemangiosarcoma treated by splenectomy with or without adjuvant chemotherapy: 208 cases (2001–2012). Journal of the American Veterinary Medical Association, 247(4), 393-403

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.

Hairballs

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

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.

• 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

I support many owners who feed homemade and raw diets, and I try to practise evidence-based healthcare. Therefore, a statistic like this deserves a closer look.

Why Are Dog Cancer Diets So Common?

In the face of a cancer diagnosis, most dog owners very quickly come across strong dietary advice online. Many vets don’t offer any other suggestions so if there’s no harm, it seems logical to try.

Plus, there are sound theoretical reasons why dogs with cancer should be fed differently.

The two most common approaches are described below. Afterwards, I’ll add my views on supplements, and finally come up with a diet recommendation.

Low Carbohydrate Cancer Diets

It’s been known for 100 years that cancer cells preferentially convert glucose into lactic acid even when other fuels are available. This is called the Warburg Effect.

This forms the basis of the most common type of anti-cancer diet. Here, we attempt to starve cancer cells of their food source by depriving the body of carbohydrates.

While good in theory, the problem with these diets is gluconeogenesis. This is where the liver takes proteins and converts them back into glucose in order to maintain blood levels. After all, the brain’s only fuel source is glucose, and without it we go into a coma.

This unavoidable process appears to greatly reduce the efficacy of low carbohydrate diets. So while it’s possible that low carb diets may slow cancer, so far we cannot see any evidence via increased or prolonged survival rates.

Ketogenic Cancer Diets

The ketogenic diet is an ultra-low carbohydrate diet where the majority of the calories come from fats. Often this is by the addition of coconut oil. The aim here is to make cancer cells more vulnerable to other treatments.

There is some low grade evidence of efficacy in humans, but significant concerns exist for dogs. This is because dogs do not tolerate high fat diets well. Pancreatitis, whether obvious or not, is likely to be very common in dogs on ketogenic diets.

For this reason, they cannot be recommended.

Cancer Diet Supplements

There are two diet supplements with some degree of evidence.

The first is fish oil, and especially its omega fatty acids DHA and EPA. Generally speaking, muscle wastage in various diseases can be partly alleviated by the addition of EFAs. Therefore, doses of 40mg/kg EPA and 25mg/kg DHA are often recommended for dogs with cancer.

Once again, care must be taken not to induce pancreatitis.

The second supplement is a polysaccharide extract of Turkeytail mushrooms, also called Trametes versicolor or Coriolus versicolor. In a very small pilot study, the ‘I’m-Yunity’ product delayed the progression of haemangiosarcoma metastases and appeared to extend survival time.

Other supplement benefits are currently unknown. These include cucurmin or turmeric, CBD, yunnan baiyao, Vitamin D, glutamine, green tea, Astragalus, melatonin, and probiotics. S-adenosylmethionine (SAMe) and silybin (milk thistle extract) are two liver support compounds that may be useful in alleviating some of the harmful effects of chemotherapy.

Negative Effects Of Cancer Diets

I also want you to consider ways that dog cancer diets can cause harm. Here are some examples:

1. They may change the taste of the food and therefore reduce food intake right when we need it. This is especially true for some supplements such as turmeric.
2. Many homemade diets and recipes promoted online are severely unbalanced. Now is not the time to be nutrient deprived. The graphic below shows an analysis we did of a widely advertised cancer diet for dogs.
3. Some supplements may actively counteract cancer treatments. A good theoretical example is antioxidants which may reduce oxidative injury to cancer cells in chemotherapy.
4. Major diet change in dogs is often associated with gastrointestinal upsets.

What Is The Best Cancer Diet?

In selecting foods for dogs with cancer, we should always follow the principle, “first, do no harm”.

I’m agnostic on clients who choose to use low carbohydrate diets as long as the dog tolerates them and the diet has been properly balanced. This is almost never true for diets available online, but can be done with the help of a veterinary nutritionist.

However, it will disappoint many people to hear that if I had a dog with cancer, I would not change the diet substantially. Food choice is unlikely to alter the course of the disease, but what will is poor nutrition or poor food intake.

I would add omega-3 at the doses mentioned earlier, and I would certainly investigate Turkeytail extract if the cancer I was fighting was prone to metastasis. This is something you could talk over with your vet but great care would be needed to find a reputable source.

How Do We Explain Miracle Cures?

Over my long career I have seen many dogs survive cancer in a way that seemed miraculous. But like everything in life, once you dig deeper, it’s not so simple.

The ‘miracle cures’ that I have seen were all the result of an initial misdiagnosis caused by the first vet not taking a biopsy. Hemangiosarcoma and osteosarcoma in particular are very hard to prove without sending samples away.

Additionally, as I mentioned under mast cell tumours, many cancers behave unpredictably. Some can appear to go into remission, even if untreated. Others don’t grow back even when they aren’t all removed.

A Realistic View?

I’m not going to criticise you for trying a new diet if your dog develops cancer. I just don’t want you to be disappointed. This comes by understanding that all we can hope to do is delay the inevitable.

What about food as a cause of cancer? Here we are on even shakier ground. The main reason that cancer is twice as common in dogs as humans appears to be genes, not diet.

Maintenance of muscle mass is vital in late stage cancer. This is probably the most important effect of the right diet together with moderate exercise. If you can achieve this without sacrificing nutrition or health, your dog’s remaining time should be as high in quality as you can make it.

Whatever diet you choose!

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.

References

Bianco, A. V., Abood, S., Mutsaers, A., Woods, J. P., Coe, J. B., & Verbrugghe, A. (2020). Unconventional diets and nutritional supplements are more common in dogs with cancer compared to healthy dogs: An online global survey of 345 dog owners. Veterinary and comparative oncology, 18(4), 706-717

Brown, D. C., & Reetz, J. (2012). Single agent polysaccharopeptide delays metastases and improves survival in naturally occurring hemangiosarcoma. Evidence-Based Complementary and Alternative Medicine, 2012

Weber, D. D., Aminzadeh-Gohari, S., Tulipan, J., Catalano, L., Feichtinger, R. G., & Kofler, B. (2020). Ketogenic diet in the treatment of cancer–where do we stand?. Molecular metabolism, 33, 102-121

Just a warning: this is no one-size fits all treatment!

What Is A Mast Cell Tumour?

Mast cell tumours (MCTs) are the second most common malignant cancer of dogs, and the most common on the skin. They can vary from a cyst-like lump under the skin to a nasty red raised mass, and affect up to 20% of dogs.

Certain breeds are more likely to develop mast cell tumours, but any dog can get them. The most at risk are:

• Boston Terriers
• Boxers
• Golden Retrievers
• Labrador Retrievers
• Pugs
• Staffies

Due to where mast cells are generally found, most tumours in dogs are located either on or just under the skin. More rarely they can be internal in the liver or spleen.

The pictures here and above give a good idea of what MCTs look like. However, there’s no way to be certain without a checkup and testing. 

Diagnosis Of Mast Cell Tumours

MCTs are one of the rare tumours where it’s possible to make a rapid diagnosis at the first visit. A simple fine needle aspirate (FNA) or needle biopsy is all it takes. Once stained and examined by your vet or a pathologist, it can show the characteristic granules inside the cells.

A better, but more invasive test is the incisional biopsy. This is where a small piece is cut out for laboratory analysis. Unlike an FNA, this will require at least a sedation and local anaesthetic. I’ll comment later on when this might be a good idea.

When vets are concerned that the tumour could have spread, they will recommend an ultrasound of the abdomen. They will also want to FNA and possibly remove local lymph nodes.

The benefit of all these tests is that we end up knowing a lot more about the tumour before we try to treat it.

Treatment Of Mast Cell Tumours

There are now four ways to treat mast cell tumours in dogs:

1. Surgical removal
2. Chemotherapy & radiotherapy
3. Tyrosine kinase inhibitors
4. Intratumoural injection

The choice of treatment will depend on the tumour’s location, its grade and the owner’s wishes. I’ll go through each in turn.

Surgical Removal

Whenever possible, surgical removal remains the treatment of choice. For solitary MCTs, removal is usually curative. This is possible for the vast majority of dogs. The local lymph node is also removed at the same time if there is suspicion of spread.

However, there are still two related decisions: whether to biopsy and how big the margins need to be. Margins are the rim of normal tissue we remove in order to take out microscopic tumours away from the main mass.

The size of the margins depends on the grade, or aggressiveness of the tumour. Therefore, a biopsy first is always a good idea, and especially in places where a larger margin is going to require planning or referral, such as for high-grade tumours on the legs or head.

On the other hand, for owners wishing to save the extra step, a biopsy is less important in areas where taking a good margin will be easy, like the first picture. This is especially true if the mass has been growing slowly and not causing any trouble.

Margin Size

There is a lot of debate about how big the margins need to be. The current consensus is called modified proportional margins where the margin is the same as the diameter of the tumour, with a minimum of 5mm, a maximum of 2cm, and one fascial plane deep.

Regardless of how successful we think the surgery was, the surgical site and local lymph nodes should always be watched afterwards. MCTs are well known to regrow even after supposedly ‘complete’ removal.

Lab Analysis

The main thing is to always get the tumour graded and the margins checked by a pathologist. This costs around $200 but is money well spent. Then if tumour is found near to the edges, or the MCT is high grade, further steps can be taken.

The decision to re-operate is a tricky one. Even with contaminated margins, low grade MCTs tend not to recur, and intermediate grade tumours only regrow around 33% of the time. I would make this decision based on how practical a second surgery will be.

High grade tumours have a strong tendency to recur, and survival is greatly enhanced by a post-operative course of vinblastine. This can also be a good idea for lower grade MCTs with incomplete removal or lymph node involvement.

Non-Surgical Options

There are at least three reasons why surgery can be the wrong treatment:

1. A high grade tumour is in an area where removal isn’t possible, such as the head, legs or around the genitalia
2. The dog cannot be safely put through the anaesthetic or surgery
3. The tumour has spread elsewhere

These are the dogs who need the next three options.

Chemotherapy & Radiotherapy

Chemo is helpful for certain dogs, but results can be disappointing. A combination of vinblastine and prednisolone +/- lomustine achieves some form of improvement in around 50% of cases. Even if suppressed, tumours will tend to regrow in time.

The use of radiation on the tumour has given improved responses, but it’s not available everywhere. Removal of the primary tumour before chemo also has some benefit even in cases where the disease has spread.

Chemo is probably most useful for tumours that have spread too widely to be able to control the individual masses any more. This is also true for the next treatment.

Tyrosine Kinase Inhibitors

The first major breakthrough in MCT treatment was the development of tyrosine kinase inhibitors (TKIs). The two drugs registered for dogs are toceranib (Palladia®) and masitinib (Masivet® or Kinavet®, not available in Australia).

TKIs are much easier to administer, and can be given at home. Sadly, however, results for these drugs are not much better than chemotherapy, and often at significantly greater cost. Side effects are also generally more of a problem.

All this being said, there are many dogs for whom a TKI has allowed a significant extension in lifespan. The problem we currently have is not knowing how to predict the response before starting.

Intratumoural Injection & Stelfonta

The latest development is the use of injections directly into the MCT. This is only suitable for dogs with small numbers of lumps that are easy to inject. There have been many drugs tried, but only two seem to work.

Triamcinolone is a potent cortisone drug, and may work to suppress or shrink MCTs. There is minimal evidence, but it’s inexpensive and worth a try if funds do not allow for anything else.

Tigilanol tiglate (Stelfonta®) is a new drug derived from a Queensland rainforest tree, which is ironic considering we seemed to be the last to get it. When injected into a MCT, it caused complete remission by 28 days in 73% of cases. Around half of the remaining 27% achieved remission with a second dose and only 7.5% of all the responders suffered a relapse.

Stelfonta is registered in many countries for:

1. the treatment of non-metastatic MCT anywhere on the skin surface
2. the treatment of non-metastatic MCT under the skin at or below the elbow or hock (in trials, injections higher up caused severe complications)

This only applies to MCTs that cannot be surgically removed and have not spread.

This is a great addition. While surgical removal is still best when possible, Stelfonta can treat MCTs that up to now have required amputations or extremely disfiguring surgery. If you’re interested in Stelfonta, please also scroll down to read about its side effects.

And that’s it. I’m sorry for such a complicated story, but this is the reality of treating mast cell tumours properly. And there will still be some cases that don’t suit any of these treatments. For these, don’t panic; I have a patient right now who’s one year out from a diagnosis of untreatable MCT. He’s doing well and this could be your dog too.

However, one thing always remains the same: the earlier we see tumours, the better the chances. A small lump anywhere can usually be removed, but once they grow you’ll quickly run out of easy options.

We’re lucky to be living in an age of innovations, and so are your dogs. But we still hope you won’t need them.

Also Read: Pictures of Common Lumps Found On Dogs Skin | Types Of Lumps Found Under The Skin

Image at the start by Joel Mills, CC BY-SA 3.0, via Wikimedia Commons.

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.

References

1. Case, A., & Burgess, K. (2018). Safety and efficacy of intralesional triamcinolone administration for treatment of mast cell tumors in dogs: 23 cases (2005–2011). Journal of the American Veterinary Medical Association, 252(1), 84-91
2. Chu, M. L., Hayes, G. M., Henry, J. G., & Oblak, M. L. (2020). Comparison of lateral surgical margins of up to two centimeters with margins of three centimeters for achieving tumor-free histologic margins following excision of grade I or II cutaneous mast cell tumors in dogs. Journal of the American Veterinary Medical Association, 256(5), 567-572
3. Grant, J., North, S., & Lanore, D. (2016). Clinical response of masitinib mesylate in the treatment of canine macroscopic mast cell tumours. Journal of Small Animal Practice, 57(6), 283-290
4. Hahn, K. A., Legendre, A. M., Shaw, N. G., Phillips, B., Ogilvie, G. K., Prescott, D. M., … & Hermine, O. (2010). Evaluation of 12-and 24-month survival rates after treatment with masitinib in dogs with nonresectable mast cell tumors. American journal of veterinary research, 71(11), 1354-1361
5. Jones, P. D., Campbell, J. E., Brown, G., Johannes, C. M., & Reddell, P. (2021). Recurrence‐free interval 12 months after local treatment of mast cell tumors in dogs using intratumoral injection of tigilanol tiglate. Journal of veterinary internal medicine, 35(1), 451-455
6. London, C. A., Malpas, P. B., Wood-Follis, S. L., Boucher, J. F., Rusk, A. W., Rosenberg, M. P., … & Michels, G. M. (2009). Multi-center, placebo-controlled, double-blind, randomized study of oral toceranib phosphate (SU11654), a receptor tyrosine kinase inhibitor, for the treatment of dogs with recurrent (either local or distant) mast cell tumor following surgical excision. Clinical Cancer Research, 15(11)
7. Selmic, L. E., & Ruple, A. (2020). A systematic review of surgical margins utilized for removal of cutaneous mast cell tumors in dogs. BMC veterinary research, 16(1), 1-6
8. Smrkovski, O. A., Essick, L., Rohrbach, B. W., & Legendre, A. M. (2015). Masitinib mesylate for metastatic and non‐resectable canine cutaneous mast cell tumours. Veterinary and comparative oncology, 13(3), 314-321
9. Weishaar, K. M., Ehrhart, E. J., Avery, A. C., Charles, J. B., Elmslie, R. E., Vail, D. M., … & Thamm, D. H. (2018). c‐Kit mutation and localization status as response predictors in mast cell tumors in dogs treated with prednisone and toceranib or vinblastine. Journal of veterinary internal medicine, 32(1), 394-405

Side Effects Of Stelfonta

The major side effect of Stelfonta is the development of an open wound at least the size of the tumour, which can also be painful for a few days. In rare causes, these wounds are very big indeed. You can see pictures of some in the USA product insert.

The wounds generally heal without complications and leave minimal scarring or disfigurement. Wounds appear to be larger when the tumour has spread, so checking the local lymph node before treatment seems almost essential.

Another potential adverse effect is caused by the release of histamine from mast cells. Deaths occurred in early trials, but these seem to be prevented by pre-treatment with steroids, antihistamines and antacids. Therefore this is also essential.

• Is my dog is at risk of skin cancer?
• What do I look out for?
• What do I do if it happens?

By ‘skin cancer’ I mean only those tumours caused by sun exposure. Visit this page if you want to see a larger list of lumps on dogs’ skin.

Dogs Breeds Prone To Skin Cancer

Any dog with areas of pink skin lacking pigment is at risk. Common examples are:

• American Staffy
• Border Collie
• Boxer
• Bull Terrier
• Dalmatian
• Jack Russell Terrier
• Staffordshire Bull Terrier

The second crucial factor is the amount of ultraviolet exposure. That means skin cancer is rare in dogs in the UK and northern Europe, and common in dogs allowed to sunbathe throughout the Americas, Africa, Australia and New Zealand.

The picture above shows a simple guide to see if your dog is at high risk. Lightly pinch an area of pink skin, and compare the width of the fold to an area of black skin. If the pink skin is thicker, it’s telling you your dog’s skin is being damaged. You need to act.

Types Of Skin Cancer & Pictures

There are only two common types of skin cancer caused by the sun. They mainly occur in areas with little or no hair coverage, mostly on the belly and inner thighs.

Squamous Cell Carcinoma

Squamous cell carcinoma, or SCC, is the most common and serious. Because it rarely forms a lump it fools dog owners into thinking it’s just a wound or injury.

An early stage SCC looks like any small skin cut, except that it doesn’t heal. There is usually a dark scab over the top like the first picture. Note that it sits in the pink, unpigmented area, not the black spots.

As they grow they often become raw and open, with an ulcerated surface. The second image shows the classic appearance of a circular wound with a distinct edge, quite unlike the ragged edge of a cut or scrape.

This photo shows an SCC that has been left too long. Letting it get this big risks it spreading into the local lymph nodes, from where it’s difficult to stop.

Although there’s no guarantee, it should still be OK as long as it’s taken out soon.

Cutaneous Haemangioma

When small, a haemangioma looks like a small red bump or berry. Here’s one pictured on a dog’s leg, again starting in the pink skin.

Unlike SCC, a haemangioma (hemangioma in the USA) rarely spreads to the lymph nodes. However, they are often rapid-growing and can still cause death if left too long.

They also have another unpleasant feature. As haemangiomas enlarge, their surface breaks open and bleeds with even the slightest knock. Such an example is shown in the second image.

Once again, this can still be safely removed. Note also how unhealthy the rest of the pink skin looks due to years of solar radiation.

Other Skin Cancers

Unlike in people, a melanoma on a dog’s skin is rarely caused by sun exposure. They are also far less likely to spread or metastasise. Most should still be removed, especially on sensitive places like the head or legs.

You can read here about melanomas in the mouth of dogs, which have very different behaviour. Other skin lump pictures can be found here.

Prevention Of Skin Cancer

Once skin cancer appears, there is no good alternative to speedy removal, so I won’t discuss this further. Much more important is preventing skin cancer.

Step 1: Get your dog out of the sun. Whenever the UV index is at 3 or greater, skin damage is likely. This is when susceptible dogs should be kept in the shade or inside.

You can’t trust dogs to do the right thing, especially on those cool, sunny days in late spring and early summer. It’s not only smart, it’s cost-effective to build a shady fenced area if your dog is a sunbather. What ends up causing the death of many dogs is the unsustainable financial burden of repeated operations.

Step 2: Use sunscreen. Here’s Loki’s nose. The pink area gets a dab of sunscreen . He also has a lot of pink skin underneath, but it’s not very practical to put creams there due to the way it picks up dirt. However, if you’re prepared to bath your dog each time, it’s fine there too.

Step 3: Sun shirts. Personally, I think these are very hard to do well, as the highest risk area is the hardest to cover. If you can fit one that covers the groin but still allows for urination and doesn’t just ride up each time they lie down, then go for it.

A normal hair coat protects the skin almost as well as a shirt. This is a reminder to be especially careful if you’ve shaved your dog for summer.

The main message is (of course) to get those small lesions checked before they become large ones. Have a safe summer!

Related: Common Pet Emergencies Of The Summer Holidays

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By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. Meet his team here.

He was a Bernese Mountain Dog with enlarged lymph nodes, and I knew he had cancer in the same way I know it when:

• a Rottweiler limps in a certain way
• a German Shepherd suddenly goes pale and weak, or
• a Staffie gets a lump on the leg

I hate this. I really hate the inevitability of it all. Because the fact that vets can draw links between breeds and cancers is anything but random.

It goes to the heart of why dogs get so much cancer.

The Number 1 Cause Of Cancer In Dogs

It’s staring us right in the face. It’s their genes.

Not pesticides, or whether they’re desexed, or processed foods. Yes, we know that cancers can have other risk factors, but these all seem insignificant when compared with the genetic ones.

Any time a disease is more common in one dog breed than another, part of the reason has to be in their DNA. Yet like so many genetic diseases of dogs, we take it for granted that it has to be that way. It doesn’t.

Why Cancer Is Common In Certain Dogs

The cancers we’re talking about have their origin in a genetic mutation, which was probably present from birth. There are plenty of human equivalents, but they aren’t the same. In a human population, each faulty gene is generally uncommon, and each carrier probably only has one copy.

Compared to humans, purebred dogs are all inbred.

Once upon a time dogs were just dogs in all their shapes and sizes. Then around 200 years ago, each of the breeds was defined and isolated, often from a small number of founders.

To be a purebred dog, you need to show that you’re only descended from these dogs. To make matters worse, we have:

• frequent use of popular sires
• inbreeding practices 
• population bottlenecks (such as in WWII)

All of which further reduce genetic diversity. Meaning that in certain breeds, mutations that were formerly rare become common, and some individuals even end up with two copies.

The Dog Breeds Prone To Cancer

The rate of cancer in dogs is not evenly spread. There are some breeds that hardly get cancer until they’re old, and others for whom it’s far too common. I want to share with you three big studies with dog cancer statistics.

In each case the number refers to the percent of dogs of that breed who died of cancer. In each case I only show the dogs with above average risk.

First, this study of insured Swedish dogs.

Second, this study from the USA containing more breeds.

And lastly, this UK study that contains one extra statistic.

You can see that certain breeds reappear in each study, and others only appear once. These might be breeds only popular in one place, or breeds where the risk varies between countries. Or it might just be chance.

The UK study adds an important point: it matters much more if a dog dies of cancer at 8 than if they died of it at 13.

Are Cancer Rates In Dogs Increasing?

There are several reasons why it might seem that cancer in dogs is getting more common.

1. Cancer rates are actually increasing
2. Dogs are living longer lives, and so cancer will be a greater cause of death
3. Dogs receive better veterinary care, and therefore more accurate diagnosis

I think the true reason is a mix of all three. I believe that the giant breeds are getting more cancer due to their increased size. I also think that it’s hard to deny the loss of genetic diversity with each generation.

But I also have seen the advances in both how pet owners look after their dogs, and how vets can treat them. For that reason, I’m not too alarmed. But I would dearly like to see more breeders of high-risk breeds making an effort to select for dogs less likely to die early of cancer.

Yes it will be hard. It would mean either choosing family lines that have had fewer cancers in the past, or identifying the faulty genes and testing before breeding.

The statistics tell us it’s possible.

Related: Lifespans Of Dog Breeds | How To Help Your Dog Live Longer

References

Bonnett, B. N., Egenvall, A., Hedhammar, Å., & Olson, P. (2005). Mortality in over 350,000 insured Swedish dogs from 1995–2000: I. Breed-, gender-, age-and cause-specific rates. Acta Veterinaria Scandinavica, 46(3), 105

Fleming, J. M., Creevy, K. E., & Promislow, D. E. L. (2011). Mortality in North American dogs from 1984 to 2004: an investigation into age‐, size‐, and breed‐related causes of death. Journal of Veterinary Internal Medicine, 25(2), 187-198

Adams, V. J., Evans, K. M., Sampson, J., & Wood, J. L. N. (2010). Methods and mortality results of a health survey of purebred dogs in the UK. Journal of Small Animal Practice, 51(10), 512-524

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By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. Meet his team here.

While the paper isn’t perfect (more on that later), it does provide the first evidence for Yorkies on choosing a time of desexing with the fewest health problems. The study compared dogs neutered at different ages for their rates of:

• hip dysplasia (HD), cruciate ligament injury (CCL) and elbow dysplasia (ED)
• lymphoma (LSA), mast cell tumour (MCT), haemangiosarcoma (HSA), osteosarcoma (OSA)
• urinary incontinence (UI)

All of these have been suspected to be linked with the age of neutering. Here’s what they found (only bold values are significant, my summary to follow):

UI was not reported in any of the spayed females.

If this table makes no sense, it’s mostly because there are no abnormal findings. Have a look at this one for Golden retrievers as a comparison. 

Summary: The Best Yorkshire Terrier Spay & Neuter Times

There is minimal evidence that Yorkie health problems are influenced by the age of neutering. Owners of either sex are therefore free to choose the age of desexing that suits them best.

Recommendation: 6 months for both sexes.

This is so far the only science we have for the best desexing age in Yorkies. Your vet, breeder or online group may have a different opinion based on their experience or personal beliefs. It’s perfectly reasonable to take their advice into consideration as well.

Problems With This Study

The authors do not mention the well-known increase in lifespan associated with desexing male and female dogs, which tends to counteract most concerns about specific cancers. The following comment in the paper is a clue that it might also have been true for this population:

Across all breeds the mean age of last entry in the record for neutered males was 5.5 years (range 3.71–6.54), for neutered females 5.7 years (range 4.21–6.97), for intact males 4.9 (range 4.15–7.11), and intact females 4.7 (range 3.41–6.32)

The study tries to also look at the rates of mammary cancer & pyometra in females, but cannot give an accurate assessment for two reasons:

1. the mean ages listed above are far too young to pick up most cases
2. pyometra and mammary cancer are rarely referred to university hospitals

Regardless of any concerns, the authors are to be applauded to bringing into focus one of the most common questions from dog owners. For the Yorkshire Terrier at least, they’ve made the decision a lot easier.

Related: Best Desexing Age For 35 Breeds | Desexing Choices For Dogs | Costs Of Desexing

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By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. Meet his team here.

While the paper isn’t perfect (more on that later), it does provide the first evidence for Westies on choosing a time of desexing with the fewest health problems. The study compared dogs neutered at different ages for their rates of:

• hip dysplasia (HD), cruciate ligament injury (CCL) and elbow dysplasia (ED)
• lymphoma (LSA), mast cell tumour (MCT), haemangiosarcoma (HSA), osteosarcoma (OSA)
• urinary incontinence (UI)

All of these have been suspected to be linked with the age of neutering. Here’s what they found (only bold values are significant, my summary to follow):

There was a single case of UI in the females spayed < 6 months and in those spayed 6-11 months.

If this table makes no sense, it’s mostly because there are no abnormal findings. Have a look at this one for Golden retrievers as a comparison. 

Summary: The Best Westie Spay & Neuter Times

There is minimal evidence that Westie health problems are influenced by the age of neutering. Females spayed early had a higher incidence of urinary incontinence but the numbers are far too small to be meaningful.

Recommendation: 6 months for both sexes

This is so far the only science we have for the best desexing age in Westies. Your vet, breeder or online group may have a different opinion based on their experience or personal beliefs. It’s perfectly reasonable to take their advice into consideration as well.

Problems With This Study

The authors do not mention the well-known increase in lifespan associated with desexing male and female dogs, which tends to counteract most concerns about specific cancers. The following comment in the paper is a clue that it might also have been true for this population:

Across all breeds the mean age of last entry in the record for neutered males was 5.5 years (range 3.71–6.54), for neutered females 5.7 years (range 4.21–6.97), for intact males 4.9 (range 4.15–7.11), and intact females 4.7 (range 3.41–6.32)

The study tries to also look at the rates of mammary cancer & pyometra in females, but cannot give an accurate assessment for two reasons:

1. the mean ages listed above are far too young to pick up most cases
2. pyometra and mammary cancer are rarely referred to university hospitals

Regardless of any concerns, the authors are to be applauded to bringing into focus one of the most common questions from dog owners. For the West Highland White Terrier at least, they’ve made the decision a lot easier.

Related: Best Desexing Age For 35 Breeds | Desexing Choices For Dogs | Costs Of Desexing

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By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. Meet his team here.

While the paper isn’t perfect (more on that later), it does provide the first evidence for Shi Tzus on choosing a time of desexing with the fewest health problems. The study compared dogs neutered at different ages for their rates of:

• hip dysplasia (HD), cruciate ligament injury (CCL) and elbow dysplasia (ED)
• lymphoma (LSA), mast cell tumour (MCT), haemangiosarcoma (HSA), osteosarcoma (OSA)
• urinary incontinence (UI)

All of these have been suspected to be linked with the age of neutering. Here’s what they found (only bold values are significant, my summary to follow):

UI was not reported in any of the spayed females.

Summary: The Best Shi Tzu Spay & Neuter Times

There is minimal evidence that Shi Tzu health problems are influenced by the age of neutering other than an increase in cancer noted in females spayed over 12 months of age.

Recommendation: 6 months for both sexes.

This is so far the only science we have for the best desexing age in Shi Tzus. Your vet, breeder or online group may have a different opinion based on their experience or personal beliefs. It’s perfectly reasonable to take their advice into consideration as well.

Problems With This Study

The authors do not mention the well-known increase in lifespan associated with desexing male and female dogs, which tends to counteract most concerns about specific cancers. The following comment in the paper is a clue that it might also have been true for this population:

Across all breeds the mean age of last entry in the record for neutered males was 5.5 years (range 3.71–6.54), for neutered females 5.7 years (range 4.21–6.97), for intact males 4.9 (range 4.15–7.11), and intact females 4.7 (range 3.41–6.32)

The study tries to also look at the rates of mammary cancer & pyometra in females, but cannot give an accurate assessment for two reasons:

1. the mean ages listed above are far too young to pick up most cases
2. pyometra and mammary cancer are rarely referred to university hospitals

Regardless of any concerns, the authors are to be applauded to bringing into focus one of the most common questions from dog owners. For the Shi Tzu at least, they’ve made the decision a lot easier.

Related: Best Desexing Age For 35 Breeds | Desexing Choices For Dogs | Costs Of Desexing

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.

While the paper isn’t perfect (more on that later), it does provide the first evidence for Pugs on choosing a time of desexing with the fewest health problems. The study compared dogs neutered at different ages for their rates of:

• hip dysplasia (HD), cruciate ligament injury (CCL) and elbow dysplasia (ED)
• lymphoma (LSA), mast cell tumour (MCT), haemangiosarcoma (HSA), osteosarcoma (OSA)
• urinary incontinence (UI)

All of these have been suspected to be linked with the age of neutering. Here’s what they found (only bold values are significant, my summary to follow):

UI was not reported in any of the spayed females.

If this table makes no sense, it’s mostly because there are no abnormal findings. Have a look at this one for Golden retrievers as a comparison. 

Summary: The Best Pug Spay & Neuter Times

There is minimal evidence that Pug health problems are influenced by the age of neutering. Owners of either sex are therefore free to choose the age of desexing that suits them best.

Recommendation: 6 months for both sexes.

This is so far the only science we have for the best desexing age in Pugs. Your vet, breeder or online group may have a different opinion based on their experience or personal beliefs. It’s perfectly reasonable to take their advice into consideration as well.

Problems With This Study

The authors do not mention the well-known increase in lifespan associated with desexing male and female dogs, which tends to counteract most concerns about specific cancers. The following comment in the paper is a clue that it might also have been true for this population:

Across all breeds the mean age of last entry in the record for neutered males was 5.5 years (range 3.71–6.54), for neutered females 5.7 years (range 4.21–6.97), for intact males 4.9 (range 4.15–7.11), and intact females 4.7 (range 3.41–6.32)

The study tries to also look at the rates of mammary cancer & pyometra in females, but cannot give an accurate assessment for two reasons:

1. the mean ages listed above are far too young to pick up most cases
2. pyometra and mammary cancer are rarely referred to university hospitals

Regardless of any concerns, the authors are to be applauded to bringing into focus one of the most common questions from dog owners. For the Pug at least, they’ve made the decision a lot easier.

Related: Best Desexing Age For 35 Breeds | Desexing Choices For Dogs | Costs Of Desexing

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.