Cancer in Bernese Mountain Dogs: Histiocytic Sarcoma & Warning Signs

By the Riverside Berner Guide editorial team
Last updated November 7, 2026

Bernese Mountain Dog cancer is the breed’s biggest health threat. In the BMDCA’s 2005 health study, 67% of the dogs that died died of some form of cancer, and the most common type is histiocytic sarcoma. You can’t prevent it with certainty, but you can learn the warning signs, understand what the breed’s risk test means, and get to your vet early.

This guide explains the cancers seen most often in Berners and what current research is finding. It doesn’t diagnose or treat anything. If you notice a sign that worries you, ask your vet.

Bernese Mountain Dog cancer: how common is it?

Cancer shows up again and again in Berner health data. Besides the 2005 study figure above, the club’s page on the histio risk test says histiocytic sarcoma alone kills more than 16% of Bernese Mountain Dogs. A 2012 genetics study put the share of the breed affected by it at 15% to 25%.

Part of the risk is inherited. The BMDCA’s Health Issues sheet says at least two cancers are inherited in Berners: mast cell cancer and histiocytic sarcoma. It adds that the exact pattern isn’t known, but several genes are suspected to work together.

Cancer is also a big reason Berners have short lives. The same sheet says dogs in the club’s most recent health report lived to between seven and eight years on average. Our guide to Bernese lifespan looks at the other causes and what helps.

Histiocytic sarcoma: the breed’s most common cancer

The BMDCA’s Diseases & Conditions page calls histiocytic sarcoma the most common cancer in the breed and says it has been shown to be inherited. You may also see it called malignant histiocytosis, its former name.

What it is

Histiocytes are immune cells found in the lymph nodes and organs. Histiocytic sarcoma is an aggressive cancer of these cells, and the club’s risk test page describes three forms:

• Localized: It starts in one place, most often bones, joints, skin or lungs.
• Disseminated: It affects several organs or tissues at the same time.
• Hemophagocytic: It starts in the spleen and moves quickly.

Who gets it and when

A French study of affected Berners looked closely at 89 dogs. Their average age at diagnosis was about 6.5 years, with a range of 2 to 11 years, and about 70% were diagnosed between ages 5 and 8. Males and females were affected at about the same rate.

In that study, 82% of the dogs had cancer in internal organs, mainly the spleen, lungs, lymph nodes and liver. That helps explain why early signs can be easy to miss. The most common signs at diagnosis were general ones: poor appetite (92%), weakness (90%) and weight loss (88%).

Why the outlook is hard

The BMDCA’s risk test page states that no effective treatment exists yet and that the disease is fatal. In the French study, most affected dogs lived only weeks after diagnosis. If your dog is diagnosed, ask your vet about every option, including a referral to a veterinary cancer specialist.

Other cancers seen in Berners

Histiocytic sarcoma isn’t the only cancer on the club’s list. The Diseases & Conditions page also describes these:

• Mast cell tumors. These make up as many as 25% of skin tumors in dogs, and about half are malignant. They usually look like raised lumps that feel soft to firm, often on the body and legs, and appear on average around age 8.5. The club believes heredity plays a role.
• Lymphoma. This cancer can affect the lymph nodes, bone marrow, liver and spleen. There are several types, and it can occur at any age.
• Hemangiosarcoma. This is a cancer of blood vessel cells. The tumors fill with blood, and a rupture can be life-threatening right away.

These cancers may share some genetic roots. A 2021 study in PLOS Genetics found that several gene regions linked to histiocytic sarcoma in Berners were also linked to lymphoma and mast cell tumors.

Does spay or neuter timing matter?

A 2020 study of 235 Berners looked at four cancers: lymphoma, hemangiosarcoma, mast cell tumors and bone cancer. About 9% of intact males and 9% of intact females had at least one of them. Females spayed before 6 months had about twice that rate, while neutering males showed no clear increase.

That study didn’t include histiocytic sarcoma. Timing is a medical decision with trade-offs for joints too, so ask your vet, and see when to spay or neuter a Bernese.

Dog cancer symptoms to take to your vet

The BMDCA’s cancer page lists ten common signs of cancer in small animals, and Cornell’s cancer FAQ gives a similar list:

• A lump or swelling that stays or keeps growing
• A sore that won’t heal
• Weight loss you can’t explain
• Loss of appetite
• Bleeding or discharge from any body opening
• A bad smell
• Trouble eating or swallowing
• Less stamina or not wanting to exercise
• Lameness or stiffness that doesn’t go away
• Trouble breathing, peeing or pooping

Lumps: don’t guess

Most lumps aren’t cancer. NC State’s veterinary college says up to 80% of skin lumps in pets are benign, but a vet visit is the only way to be sure. It suggests calling your vet if a lump grows or hasn’t gone away within a few weeks.

Vague signs count too

The same NC State page says sudden weight loss in a pet that isn’t dieting is a reason to call your vet right away. It also lists coughing, low energy, more sleep and changes in bathroom habits as possible signs. Remember that Berners with histiocytic sarcoma often first showed only a poor appetite, weakness and weight loss.

NC State also warns never to give your dog human pain medicine, because many are deadly for pets. If your dog seems to hurt, ask your vet.

Why early matters

The BMDCA’s cancer page says finding cancer early improves the chance of survival. It also notes that the club’s health committee can’t diagnose dogs or advise on cancer care, so rely on your own vet.

The histiocytic sarcoma risk test: what results mean

The BMDCA recommends a genetic risk test for histiocytic sarcoma, sold through a lab called Antagene. It’s one of three optional tests in the club’s Berner Recommended Testing program, alongside thyroid and von Willebrand disease. The club’s instructions say a vet draws the blood sample.

A, B and C results

The test looks at nine genetic markers linked to the cancer. The BMDCA’s pre-test page explains the three results:

• A: about four times less likely to develop histiocytic sarcoma
• B: neither more nor less likely than average
• C: about four times more likely to develop it

What the results don’t mean

The same page is clear that this is not a diagnostic test. An A dog may still die of histiocytic sarcoma, and a C dog may live into double digits without ever getting it. The letter doesn’t measure a dog’s worth either.

It also warns that removing every B and C dog from breeding would harm the gene pool. Instead, breeders use an Antagene tool that predicts what share of A, B and C puppies a planned mating would produce. The club says that tool should not be the only basis for breeding choices.

What this means for you

If you’re buying a puppy, ask the breeder whether the parents were tested and how they used the results. Individual letter results stay confidential in Berner-Garde, which only shows that a dog was tested, according to the BMDCA. Our guides to Bernese health clearances and finding a reputable breeder cover the other tests to ask about.

If you already have a Berner, a test result won’t change what you should watch for. The signs above still apply to every dog, whatever its letter.

Current research and how you can help

Owners and researchers have been working on this problem for years, and your dog’s records can help.

The Berner-Garde and MSU repository

The Berner-Garde Foundation runs a DNA and tissue bank in partnership with Michigan State University. Its repository page reports more than 3,500 blood samples and more than 450 frozen tumor samples. Work with researchers in France, at the NIH and at MSU has helped build ways to assess inherited cancer risk, find possible therapies for histiocytic sarcoma and explore early detection through what’s called a liquid biopsy.

General submissions of blood, tumors and litters are being suspended, and only selected dogs are being sought. The foundation says the most useful thing owners can do now is keep their dogs’ health records up to date.

Genetic studies

A 2012 study was the first genome-wide search for histiocytic sarcoma genes in any species. It found one stretch of DNA, covering a gene called MTAP and part of a gene called CDKN2A, in 96% of affected Berners. The 2021 PLOS Genetics study found several more regions, and the risk seemed to add up as a dog carried more of them.

The BMDCA’s pre-test page says the search for the genes behind the disease is ongoing at the NIH. It calls today’s test a better tool than breeders had before, but not the final answer.

Studies that need Berners now

The BMDCA’s research page lists projects that want participants, including:

• A clinical trial of a drug called trametinib for dogs with histiocytic sarcoma, run by Michigan State, the University of Wisconsin-Madison and the University of Florida
• A urine-based cancer detection project that is looking for 250 Berners with suspected or diagnosed cancer, with a free kit and no vet visit needed
• Repository samples from veteran Berners aged 12 or older

Whether a trial is right for your dog is a question to ask your vet. Studies change over time, so check the club’s page for the current list.

What you can do today

You can’t control your dog’s genes, but you can make choices that help:

• Pick a breeder who tracks cancer. Ask about the lifespan and cause of death of dogs in the pedigree, and check the family in Berner-Garde.
• Know your dog’s normal. Feel for new lumps when you groom, and notice changes in appetite, energy and weight.
• Keep regular vet visits. Ask your vet how often your Berner should be seen as they get older.
• Report to Berner-Garde. Add health events and, one day, the cause of death. Each record makes the database more useful for the next family.

The BMDCA’s cancer page also points to healthy food, exercise and a low-stress home as everyday steps. For the full picture of Berner health, including hip and elbow dysplasia, start with our guide to Bernese Mountain Dog health problems.