Cancer in Bernese Mountain Dogs: What Every Berner Owner Should Know

Bernese Mountain Dogs carry one of the heaviest cancer burdens of any dog breed. In a Swiss study of Berners born in 2001 and 2002, neoplasia was recorded as the cause of death in 222 of 381 dogs, or 58.3%, and the median life expectancy of the group was 8.4 years (Klopfenstein et al., 2016). A Dutch study reached a similar conclusion, finding that at least 55.1% of Berner deaths were associated with malignant tumors (Erich et al., 2013).

The cancer that sets this breed apart is histiocytic sarcoma, an aggressive tumor of immune cells that is uncommon in most dogs but strikingly frequent in Berners. It has been estimated to affect roughly 25% of the breed (Abadie et al., 2009). Lymphoma and osteosarcoma are also recognized causes of death in Berners (Klopfenstein et al., 2016).

None of this means your Berner will get cancer. It means that vague signs like tiredness, a poor appetite, or a new limp deserve a faster veterinary visit in this breed than they might in others.

Key Points

• Cancer is the leading recorded cause of death in Bernese Mountain Dogs, with published studies attributing roughly 55% to 58% of deaths to tumors (Erich et al., 2013; Klopfenstein et al., 2016).
• Histiocytic sarcoma is the signature cancer of the breed, and in Berners it is more often disseminated, meaning spread through multiple organs, than localized to one spot (Erich et al., 2022).
• The typical Berner with histiocytic sarcoma is middle-aged, around 6.5 years old at diagnosis, but cases have been documented in dogs younger than one year (Abadie et al., 2009; Erich et al., 2022).
• Early signs are usually vague: lethargy, poor appetite, pale gums, weight loss, and fever were each seen far more often than a visible lump (Erich et al., 2022).
• Previous joint disease has been associated with histiocytic sarcoma developing in or around that same joint in Berners, so a swelling near an old injury deserves attention (van Kuijk et al., 2013).
• The breed's risk is heritable, and a DNA risk test exists, but it is designed to guide breeding decisions and cannot tell you whether an individual dog will or will not develop cancer (Bernese Mountain Dog Club of America, n.d.; Padgett et al., 1995).

Detailed Explanation

How Much Cancer Are We Actually Talking About?

The honest answer is "a lot," with some uncertainty about exactly how much.

Klopfenstein et al. (2016) followed a Swiss birth cohort almost to completion, so nearly every dog in the study had died by the end. Neoplasia accounted for 58.3% of deaths. The authors were candid about a weakness in their own data, though: most of those cancer diagnoses were never confirmed by cytology or histopathology, and over 20% of the dogs died without any specific diagnosis at all. They concluded that the true rate of cancer could be somewhat lower or higher than what they recorded.

That caveat matters, and it cuts both ways. Some dogs recorded as having cancer may have had something else. Some dogs recorded as "unknown" almost certainly had cancer nobody confirmed.

The Dutch data point the same direction. Erich et al. (2013) found that at least 55.1% of Berner deaths were associated with malignant tumors, and that more than one in seven Berners died specifically because of histiocytic sarcoma.

Berners also die younger than dogs of comparable size. The Swiss authors noted that earlier studies placed Berner life expectancy between about 7 and 8 years, compared with breeds like flat-coated retrievers and German Shepherds living into their tenth year or beyond, and they identified the high rate of cancer as a major reason (Klopfenstein et al., 2016).

Histiocytic Sarcoma: The Berner Cancer

Histiocytic sarcoma is a malignant tumor of histiocytes, a family of immune cells that includes dendritic cells and macrophages. Because these cells live throughout the body, the tumor can arise in almost any organ (Erich et al., 2022).

It comes in two broad forms. Localized histiocytic sarcoma involves a single organ, sometimes with its nearby lymph nodes. Disseminated histiocytic sarcoma involves multiple organs or spreads beyond the regional lymph nodes (Erich et al., 2022).

This distinction is central to understanding the disease in Berners. In a study of 365 Bernese Mountain Dogs with histiocytic sarcoma, 60.8% had the disseminated form, compared with 39.4% of flat-coated retrievers, the other breed most affected (Erich et al., 2022). Berners tend to get the more widespread version.

The frequency is what makes this breed unusual. An older study of 500 tumors in Berners found that histiocytosis accounted for 25.4% of them, while the same disease was rare in eight other breeds examined (Padgett et al., 1995). Estimates of how many Berners develop histiocytic sarcoma over a lifetime vary.

French researchers put it at approximately 25% (Abadie et al., 2009), Dutch data found over one in seven Berners dying of it (Erich et al., 2013), and it was the most commonly confirmed cancer in the Swiss cohort (Klopfenstein et al., 2016). The exact figure depends on the population and on how rigorously diagnoses were confirmed, but every one of those numbers is far higher than what is seen in dogs generally.

Age at Diagnosis

Histiocytic sarcoma in Berners tends to strike in middle age. The mean age at onset was 6.5 years in one French series of 89 cases (Abadie et al., 2009), and 6.6 years in the larger Dutch and European series, where affected Berners ranged from 0.6 to 12.2 years old (Erich et al., 2022). The same study noted that Berners were diagnosed significantly younger than flat-coated retrievers.

That lower end of the range is worth pausing on. Erich et al. (2022) reported an exceptional case diagnosed at seven months of age, and their conclusion was blunt: in Berners, even from a young age, histiocytic sarcoma belongs on the list of possibilities when a dog shows general, nonspecific illness.

What Histiocytic Sarcoma Looks Like at Home

Owners often expect cancer to announce itself as a lump. In Berners with histiocytic sarcoma, that is usually not how it starts.

Among 365 Berners with the disease, the most common signs recorded at diagnosis were lethargy (58.9%), loss of appetite (56.7%), pale gums (41.4%), weight loss (36.2%), fever (25.3%), and lameness (23.8%). Coughing was recorded in 11.2% and difficulty breathing in 10.4% (Erich et al., 2022). A smaller number of dogs showed neurologic signs such as weakness or paralysis of the limbs, wobbliness, or abnormal eye movements.

Those are vague signs, and most of them have many possible causes. That is exactly why they get dismissed. A Berner who is "just a bit quiet" and "a little picky with food" for a week may be a dog in the early stages of a disease that moves fast.

Where tumors could be located in this study, Berners more often had disease in the abdomen and chest than on the limbs. When the spleen was involved, a diffuse pattern throughout the organ was far more common in Berners than in flat-coated retrievers, and the lungs and chest lymph nodes were frequent sites (Erich et al., 2022). Among Berners with tumors on a limb, the stifle, or knee joint, was the most frequently affected joint.

What the Bloodwork May Show

Anemia was the most common blood abnormality in dogs with histiocytic sarcoma, present in about three quarters of the dogs that had blood testing (Erich et al., 2022). Berners in particular often had elevated white blood cell counts and low platelet counts. Elevated blood calcium was found in 15 of 53 Berners tested and in none of the flat-coated retrievers, a finding the authors described as striking (Erich et al., 2022).

About one in four Berners with histiocytic sarcoma in that study did not have anemia when tested. A normal blood count does not mean cancer is absent. If your dog has symptoms and the bloodwork comes back unremarkable, that result narrows the possibilities without closing the question.

The Joint Connection

Berners are prone to orthopedic problems, and research suggests that joint disease and histiocytic sarcoma may be linked in this breed.

A European study of 920 Berners identified 226 dogs with joint disease. Of those, 15 later developed histiocytic sarcoma around a joint that had previously been diseased, compared with 3 that developed it around a joint with no prior disease (van Kuijk et al., 2013). The authors advised Berner owners to watch for swellings around joints, particularly joints that have had problems before.

A separate American study surveyed owners of Berners registered with the Berner-Garde Foundation, comparing dogs with histiocytic sarcoma to their unaffected littermates. Dogs diagnosed with an orthopedic condition were about 2.5 times more likely to develop histiocytic sarcoma, while dogs that had received prescription anti-inflammatory medications were at considerably lower risk (Ruple & Morley, 2016). The authors interpreted this as evidence that inflammation may be a modifiable risk factor.

That is an interesting finding, and it is also easy to over-read. This was a survey-based association study, not a treatment trial, and it does not show that giving anti-inflammatory drugs prevents cancer. Anti-inflammatory medications carry their own risks and should only be used under your veterinarian's direction for a diagnosed condition. What the research does support is taking your Berner's joint problems seriously and getting them properly treated rather than letting chronic inflammation go unmanaged.

It also means a limp in a Berner is not automatically "just the old cruciate acting up." A new swelling around a joint, or lameness that changes character, warrants a recheck rather than an assumption.

Why Berners? The Genetics

The breed's risk is inherited. As early as 1995, researchers tracing Berner pedigrees found multiple affected dogs within the same litters, repeated cases from the same sires and dams, and a higher rate of disease among offspring of affected parents. They estimated the heritability of the trait at 0.298 (Padgett et al., 1995).

Since then, the picture has become more detailed without becoming simple. Genome studies have identified a region containing the MTAP and CDKN2A genes as a major susceptibility locus in Berners (Shearin et al., 2012). The inheritance pattern appears to involve several genes rather than one, which is why no single test can sort dogs neatly into "will get it" and "won't" (Abadie et al., 2009; Bernese Mountain Dog Club of America, n.d.).

There is a second, separate layer of genetics that owners sometimes confuse with the first. Researchers have found mutations in a gene called PTPN11 inside the tumors themselves. One study found these mutations in the histiocytic sarcomas of 41 of 96 Berners, or 43% (Takada et al., 2019), building on earlier work that first identified the mutation in the breed (Thaiwong et al., 2018). These are changes that occur within the cancer cells, not inherited mutations your dog was born with. They matter for research into targeted therapies and diagnosis, but they are not what a breeding risk test measures.

The Histiocytic Sarcoma Risk Test

A DNA pre-test for histiocytic sarcoma is available through the laboratory Antagene and is discussed by the Bernese Mountain Dog Club of America. It is a risk test rather than a direct test for a disease-causing mutation. It uses nine genes on five chromosomes to produce a weighted result of A, B, or C. According to the club, dogs with an A result have a four times lower risk of developing histiocytic sarcoma, B is neutral, and C indicates a four times higher risk (Bernese Mountain Dog Club of America, n.d.).

The test was built for breeding decisions. The club and the test's developers stress that it should be only one of many selection criteria, that a C dog should not be removed from a breeding program on that result alone, and that preserving genetic diversity in the breed matters (Bernese Mountain Dog Club of America, n.d.).

For a pet owner, the most important thing to understand is what a result does not mean. An A result does not make your dog safe from histiocytic sarcoma, and a C result does not mean your dog will develop it. If you are choosing a puppy, asking a breeder about health testing, including this test, is reasonable. If you already have your Berner, a result is at most one more piece of context for your veterinarian, not a substitute for paying attention to symptoms.

How Histiocytic Sarcoma Is Diagnosed

Diagnosis requires looking at the cells. In the large European series, diagnoses were made by cytology, meaning a needle sample examined under a microscope, by histopathology from a tissue biopsy, or both, with immunohistochemistry used to confirm that the cells were histiocytic (Erich et al., 2022). A marker called CD18 is commonly used for that confirmation (Skorupski et al., 2007; van Kuijk et al., 2013).

Imaging usually comes alongside sampling. Chest radiographs can show lung masses and enlarged chest lymph nodes, and abdominal ultrasound is particularly important in Berners because of how often the spleen and liver are involved (Erich et al., 2022). The ultrasound patterns are not specific to histiocytic sarcoma, but given how common the disease is in this breed, certain findings, such as multiple nodules in the spleen or liver, raise the probability considerably.

Staging, meaning a structured look at where the disease is in the body, matters because localized and disseminated disease carry very different outlooks.

Treatment and What to Expect

Histiocytic sarcoma is one of the most difficult cancers in veterinary oncology to treat.

In the French series of Berners, the life span after diagnosis was estimated at 49 days (Abadie et al., 2009). That figure describes the cohort as a whole and should not be read as what happens with treatment in every dog, but it reflects how quickly the disseminated form can progress.

Chemotherapy with lomustine, also called CCNU, is one of the most studied options. In a multi-institutional study of dogs of several breeds with histiocytic sarcoma, 46% of the 56 dogs with measurable disease responded to lomustine, and median survival for all 59 dogs was 106 days. Low platelet counts and low blood albumin were associated with a poor prognosis and predicted survival of less than a month (Skorupski et al., 2007). If your Berner is prescribed lomustine, your veterinarian will monitor bloodwork, including liver values, throughout treatment. [INTERNAL LINK: lomustine and liver support article]

Localized disease is a different story. In 16 dogs with localized histiocytic sarcoma treated with aggressive local therapy, such as surgery or radiation, followed by lomustine, median survival was 568 days (Skorupski et al., 2009). That is a small study, and Berners are less likely than some breeds to have localized disease when diagnosed (Erich et al., 2022), but it shows why catching the disease while it is still confined can change the conversation.

A larger study of 180 dogs with confirmed histiocytic sarcoma, in which Berners were the most represented breed with 53 dogs, found a median survival of 170 days overall. Palliative-only treatment, disseminated disease, and concurrent use of corticosteroids were each associated with shorter survival (Dervisis et al., 2017). That corticosteroid finding is an association, and steroids may have been given to sicker dogs, but it is a reasonable topic to raise with your veterinarian before any steroid is started while a diagnosis is still pending.

Treatment decisions for this disease often come down to quality of life as much as length of life. Some families pursue chemotherapy, some choose comfort-focused care, and both are legitimate choices made out of love. The Joys of Life Scale from the Drake Dog Cancer Foundation can help you track the things that make your dog's days good and notice when that balance shifts.

Lymphoma, Osteosarcoma, and Other Cancers in Berners

Histiocytic sarcoma gets most of the attention, but it is not the only cancer in the breed.

In the Swiss cohort, among cancers that were confirmed by cytology or histology, histiocytic sarcoma was diagnosed in 23 dogs, lymphoma in 15, and osteosarcoma in 11. Leukemia, fibrosarcoma, hemangiosarcoma, mast cell tumors, and transitional cell carcinoma also appeared in smaller numbers (Klopfenstein et al., 2016). Median age at death was 7.17 years for dogs with histiocytic sarcoma, 7.32 years for dogs with lymphoma, and 8.74 years for dogs with osteosarcoma.

That same study recorded many more tumors that were never confirmed, including 45 described as multi-organ tumors, 29 lung tumors, and 14 splenic tumors (Klopfenstein et al., 2016). Given how often histiocytic sarcoma involves the lungs and spleen in Berners, some of those were likely histiocytic sarcoma, but there is no way to know. Other cancers, including hemangiosarcoma, can also produce splenic and lung masses. This is one of the practical reasons a confirmed diagnosis matters: different cancers call for different treatments and carry different outlooks.

Does Sex Matter?

The research does not agree. The Swiss study found that male Berners had a higher risk of dying from cancer overall and roughly three times the relative risk of histiocytic sarcoma compared with females (Klopfenstein et al., 2016). Other studies found males and females equally affected (Abadie et al., 2009; Erich et al., 2022). The Swiss authors acknowledged that the large number of dogs without a known cause of death added substantial uncertainty to their sex comparison. For now, the safest reading is that neither male nor female Berners should be considered low risk.

Can It Be Caught Early?

There is no proven screening program for histiocytic sarcoma, but researchers have tried. A Danish team screened healthy Berners on four occasions over two and a half years using diagnostic imaging and blood tests. They identified five dogs with early disseminated histiocytic sarcoma, four of them through imaging (Nielsen et al., 2012). That was a research program with a small number of dogs, not an established protocol, so whether periodic imaging makes sense for your individual dog is a conversation to have with your veterinarian.

What every owner can do is notice change early. Keeping a simple record of appetite, energy, weight, and anything new gives your veterinary team information they cannot get anywhere else, and it helps you see a slow decline that is easy to miss day to day. The Dog Cancer Tracker (dogcancertracker.com) is one way to keep that record in one place.

Why Your Berner's Diagnosis Helps Other Berners

The Swiss researchers concluded that diagnostic accuracy in the breed needs substantial improvement, and that more precise diagnoses are needed to improve breed health (Klopfenstein et al., 2016). The Berner-Garde Foundation maintains a breed health database used in research, including the study that identified the orthopedic association with histiocytic sarcoma (Ruple & Morley, 2016). If your Berner receives a confirmed cancer diagnosis, reporting it to the breed database is a way of turning a painful experience into information that may help future dogs.

When to Contact a Veterinarian

Go to an emergency veterinary hospital immediately if your Berner collapses, has very pale or white gums, is struggling to breathe, has a suddenly swollen belly, or becomes profoundly weak. Disseminated histiocytic sarcoma commonly involves the spleen, liver, and lungs (Erich et al., 2022), and these signs can reflect internal bleeding, severe anemia, or lung involvement that needs urgent care.

Schedule a prompt appointment, within a day or two rather than waiting a few weeks, if your Berner shows:

• Lethargy or low energy that is not explained by a recent change in activity or weather.
• Reduced appetite or pickiness that persists, even if your dog is still eating something.
• Weight loss you can feel over the ribs or see in how the collar or harness fits.
• A fever, if you have a thermometer and have taken a reading.
• A new cough or faster breathing at rest.
• A new limp, a swelling around a joint, or a change in an existing lameness, especially involving a joint that has had problems before (van Kuijk et al., 2013).
• Any new lump or a lump that is changing.
• Increased thirst, stumbling, weakness in the legs, or unusual eye movements.

In most breeds, a middle-aged dog with a week of vague tiredness might reasonably be watched for a while. In a Berner, that same week is worth a visit.

Questions to Ask Your Veterinarian

• Given my dog's breed and age, is histiocytic sarcoma on your list of possibilities for these symptoms?
• If the bloodwork is normal, what would we do next to rule cancer in or out?
• Would chest radiographs or an abdominal ultrasound be useful right now?
• If there is a mass, can we get a cytology or biopsy sample, and will the lab use immunohistochemistry to confirm the cell type?
• Is this disease localized or disseminated, and how does that change our options?
• If you are considering a steroid before we have a diagnosis, how might that affect testing or later treatment?
• What would lomustine or other chemotherapy involve, what monitoring would it need, and what outcomes are realistic for my dog specifically?
• My dog has a history of joint problems. Should we be watching any particular joint more closely?
• Would periodic imaging make sense for my dog, and at what age would you consider it?
• Is a referral to a board-certified veterinary oncologist appropriate?

References

Abadie, J., Hédan, B., Cadieu, E., De Brito, C., Devauchelle, P., Bourgain, C., Parker, H. G., Vaysse, A., Margaritte-Jeannin, P., Galibert, F., Ostrander, E. A., & André, C. (2009). Epidemiology, pathology, and genetics of histiocytic sarcoma in the Bernese mountain dog breed. Journal of Heredity, 100(Suppl. 1), S19-S27.

Bernese Mountain Dog Club of America. (n.d.). Health tests. Retrieved September 24, 2026, from https://www.bmdca.org/health-tests

Dervisis, N. G., Kiupel, M., Qin, Q., & Cesario, L. (2017). Clinical prognostic factors in canine histiocytic sarcoma. Veterinary and Comparative Oncology, 15(4), 1171-1180. 

Erich, S. A., Dobson, J. M., & Teske, E. (2022). Comparison of the clinical characteristics of histiocytic sarcoma in Bernese mountain dogs and flat-coated retrievers. Veterinary Sciences, 9(9), Article 498. 

Erich, S. A., Rutteman, G. R., & Teske, E. (2013). Causes of death and the impact of histiocytic sarcoma on the life expectancy of the Dutch population of Bernese mountain dogs and flat-coated retrievers. The Veterinary Journal, 198(3), 678-683. 

Klopfenstein, M., Howard, J., Rossetti, M., & Geissbühler, U. (2016). Life expectancy and causes of death in Bernese mountain dogs in Switzerland. BMC Veterinary Research, 12, Article 153. 

Nielsen, L. N., McEvoy, F., Jessen, L. R., & Kristensen, A. T. (2012). Investigation of a screening programme and the possible identification of biomarkers for early disseminated histiocytic sarcoma in Bernese mountain dogs. Veterinary and Comparative Oncology, 10(2), 124-134. 

Padgett, G. A., Madewell, B. R., Keller, E. T., Jodar, L., & Packard, M. (1995). Inheritance of histiocytosis in Bernese mountain dogs. Journal of Small Animal Practice, 36(3), 93-98. 

Ruple, A., & Morley, P. S. (2016). Risk factors associated with development of histiocytic sarcoma in Bernese mountain dogs. Journal of Veterinary Internal Medicine, 30(4), 1197-1203. 

Shearin, A. L., Hedan, B., Cadieu, E., Erich, S. A., Schmidt, E. V., Faden, D. L., Cullen, J., Abadie, J., Kwon, E. M., Gröne, A., Devauchelle, P., Rimbault, M., Karyadi, D. M., Lynch, M., Galibert, F., Breen, M., Rutteman, G. R., André, C., Parker, H. G., & Ostrander, E. A. (2012). The MTAP-CDKN2A locus confers susceptibility to a naturally occurring canine cancer. Cancer Epidemiology, Biomarkers & Prevention, 21(7), 1019-1027. 

Skorupski, K. A., Clifford, C. A., Paoloni, M. C., Lara-Garcia, A., Barber, L., Kent, M. S., LeBlanc, A. K., Sabhlok, A., Mauldin, E. A., Shofer, F. S., Couto, C. G., & Sørenmo, K. U. (2007). CCNU for the treatment of dogs with histiocytic sarcoma. Journal of Veterinary Internal Medicine, 21(1), 121-126. 

Skorupski, K. A., Rodriguez, C. O., Krick, E. L., Clifford, C. A., Ward, R., & Kent, M. S. (2009). Long-term survival in dogs with localized histiocytic sarcoma treated with CCNU as an adjuvant to local therapy. Veterinary and Comparative Oncology, 7(2), 139-144. 

Takada, M., Smyth, L. A., Thaiwong, T., Richter, M., Corner, S. M., Schall, P. Z., Kiupel, M., & Yuzbasiyan-Gurkan, V. (2019). Activating mutations in PTPN11 and KRAS in canine histiocytic sarcomas. Genes, 10(7), Article 505. 

Thaiwong, T., Sirivisoot, S., Takada, M., Yuzbasiyan-Gurkan, V., & Kiupel, M. (2018). Gain-of-function mutation in PTPN11 in histiocytic sarcomas of Bernese mountain dogs. Veterinary and Comparative Oncology, 16(2), 220-228. 

van Kuijk, L., van Ginkel, K., de Vos, J. P., Brearley, M. J., Butinar, J., Gielen, I., van Garderen, E., Chiers, K., & Verhoeven, P. S. (2013). Peri-articular histiocytic sarcoma and previous joint disease in Bernese mountain dogs. Journal of Veterinary Internal Medicine, 27(2), 293-299.