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June 22, 2021 – Histiocytic sarcoma (HS) is an uncommon but aggressive cancer of dogs. Histiocytes are a type of white blood cell that reside within the tissues of almost every organ in the body and are an important part of the immune system. They help get rid of invading pathogens and stimulate other cells of the immune system.

Histiocytic sarcomas develop when these specialized white blood cells begin dividing uncontrollably. Because white blood cells are found in many different tissues, HS can arise almost anywhere and spread quickly.

Histiocytic sarcoma was first described in Bernese mountain dogs in the late 1970s, but it has now been noted in many other breeds, including:

  • Flat-coated retrievers
  • Miniature schnauzers
  • Rottweilers
  • Labrador retrievers
  • Pembroke Welsh corgis
  • Golden retrievers

Histiocytic sarcoma is more common in middle-aged and older dogs, although there are reports of the disease in dogs as young as 3 years old. Males and females are affected equally.

Clinical signs, diagnosis and treatment

Unfortunately, the most common signs of HS are similar to many other diseases and include:

  • Lethargy
  • Poor appetite
  • Swelling and lameness (in cases of bone or joint involvement)
  • Coughing
  • Breathing difficulty
  • Vomiting
  • Diarrhea

Diagnosis usually is made based on a combination of clinical signs, bloodwork results, and biopsy or a fine needle aspirate of abnormal tissue. Additional tests, such as ultrasound or X-ray, often are used as adjunctive diagnostic tests and as a means of assessing the extent of disease.

Histiocytic sarcoma can take many forms, and clinical signs and prognosis vary with different subtypes. Three recognized subtypes are: localized, disseminated and hemophagocytic.

  • Localized HS is confined to one organ and usually is treated with surgery followed by chemotherapy. In many cases, patients can live more than one year (and occasionally longer), depending on the success of the surgery.
  • Disseminated HS affects many different organs. Chemotherapy can be used to slow progression of disease, but prognosis is poor with most patients only living a few months.
  • Hemophagocytic HS is the most aggressive subtype. No effective treatments exist and survival times are only one to two months.

There is evidence a genetic component may play a role in HS. The only other risk factors identified to date are a history of orthopedic disease and inflammation when HS is localized to a joint.

Histiocytic sarcoma and the Golden Retriever Lifetime Study

The Golden Retriever Lifetime Study is carefully tracking all cancers reported in our Study participants, including histiocytic sarcoma. In fact, we’ve added HS to the primary endpoint cancers in our Study (osteosarcoma, hemangiosarcoma, lymphoma and mast cell tumor), due to a higher level of occurrence than originally expected at the outset of the Study.

As of June 2021, we’ve recorded 20 cases of histiocytic sarcoma in our cohort of dogs. Our Study team is monitoring all of our cancer cases, including histiocytic sarcoma, as a first step toward looking for risk factors associated with the development of this terrible cancer.

You can help change the odds for dogs with histiocytic sarcoma and other cancers

We still have a long way to go to stop histiocytic sarcoma. Learn what you can do to improve to give hope to dogs and their people affected by this aggressive, and poorly understood, cancer.