Histiocytic Sarcoma in dogs

Histiocytic sarcoma is an aggressive cancer. It can be very invasive (destroy normal surrounding tissues) and has a high rate of metastasis (spreading to other areas of the body). Most dogs affected by this disease are middle- aged to older, although dogs of any age can be affected. 

Histiocytic sarcoma can be somewhat complex to understand as it comes in multiple forms. Localized histiocytic sarcoma is most commonly found in the spleen, lymph nodes, lung, bone marrow, skin, brain, and joints of the limbs. Disseminated histiocytic sarcoma occurs in multiple organs simultaneously. Both types can metastasize, ultimately affecting multiple organs, which is where the confusion sometimes arises

Common Symptoms

Clinical signs vary depending on the anatomic locations involved, but common nonspecific signs include:

  • Decreased appetite

  • Weight loss

  • Lethargy, weakness

  • Vomiting and diarrhea 

Other signs depend on the organs involved. For example, if there is a large mass in the lungs, a dog may experience coughing or difficulty breathing. If the brain is involved, you may see seizures, incoordination, and paralysis. If a joint is involved, lameness or limping is often seen. If the disease is localized to the skin, there may be no clinical signs or changes in behavior. You may only notice a new mass when petting your dog. Enlarged lymph nodes, an enlarged spleen and an enlarged liver are harder to detect by pet parents but can be detected by your veterinarian.

Causes and Risk Factors

The cause is largely unknown.

Breeds with high incidence of histiocytic sarcoma

HS can occur in any dog breed. However, certain breeds have a higher predisposition to this type of cancer including Bernese Mountain dogs, Flat-Coated Retrievers, Golden Retrievers and Rottweilers.


Historically, depending on the site, your vet oncologist might recommend surgery, radiation, amputation and some form of chemotherapy. Today, oncologists have more tools in their toolkit. Targeted therapies are a more advanced treatment option. FidoCure, from The One Health Company, enables your vet oncologist to understand the exact genetic mutation causing your dog’s cancer and provide an individualized, targeted treatment plan leveraging the latest science available in oncology.

DISCLAIMER: FidoCure™ is a leader in oncology research for dogs, and our team is committed to the breakthroughs in cancer biology to evolve canine cancer care, with each patient improving the outcomes for all future canine cancer patients. We use our best efforts to inform the veterinarian, who then decides which option is best for their patient. The therapies that veterinarians may prescribe and order from compounding pharmacies after receiving genetic test results from FidoCure, may constitute extra-label uses of those drugs. FidoCure is continuing to gather research data in support of novel oncology therapeutics in dogs.

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