Hemangiosarcoma, Leukemia and Lymphoma in Dogs
As we wrap up Blood Cancer Awareness Month, it’s important for pet parents to be able to recognize the signs and symptoms of these devastating diseases. Early detection is key to successful treatment of cancer in pets, which can creep in silently until it’s too late. Cancers of the blood are especially dangerous, as the disease can occur and spread to blood vessels or blood-forming organs throughout the body. Types of blood cancer in dogs include hemangiosarcoma, leukemia and lymphoma.
Hemangiosarcoma in Dogs
More common than its complicated name implies, hemangiosarcoma in dogs is an incurable tumor that occurs in the walls of blood vessels. An estimated 5 to 7 percent of dogs will develop the disease, roughly 1.5 to 2.5 million in the U.S.. Described by leading researchers as “among the most challenging and mysterious diseases encountered in veterinary practice,” its true cause is unknown. Most types of cancer in dogs have a strong genetic component and are more likely to occur in certain breeds. Although any dog can develop the disease – roughly a third to half of all pets will develop some form of cancer – senior dogs are more susceptible, as are several breeds:
- Golden Retrievers
- German Shepherds
- Labrador Retrievers
- Portuguese Water Dogs
- Bernese Mountain Dogs
Hemangiosarcoma can develop on any blood vessels or organs, most frequently appearing on the spleen. The cancer also commonly occurs on the right atrium of the heart and just below the skin, where the condition is known as dermal hemangiosarcoma. Difficult to detect, the tumors’ initial growth is slow and painless as the disease metastasizes to surrounding tissue. Oftentimes symptoms are nonexistent or nonspecific, like lethargy and weakness; tiny blood clots cause minuscule tears in the tumor, leading to minor internal bleeding. Lumps, bruises, pale gums, difficulty breathing, abdominal swelling, and seizures are also signs of hemangiosarcoma in dogs. As the cancer progresses larger ruptures can occur, leading to hemorrhage and eventual death. Tumors on organs can also cause secondary complications, like a hemangiosarcoma in the lung leading to difficulty breathing.
Unfortunately, there is no way to cure or prevent hemangiosarcoma. Life-prolonging treatment for the disease may involve surgery and/or chemotherapy, depending on the severity and location of the tumor(s). The average survival rate after treatment for hemangiosarcoma in dogs is 90 days for surgery and up to 180 days with chemotherapy and surgery. Although removal of the spleen may lengthen a pet’s life in the short term, it is not a “cure” as the cancer eventually spreads to blood vessels and other organs.
Leukemia in Dogs
Another cancer of the blood, lymphocytic is the most common type of leukemia in dogs, caused by too many white blood cells – lymphocytes – in the body. Originating in the bone marrow and spleen, lymphocytes are crucial to the immune system. The cancer can be acute, occurring suddenly and severely, or chronic and long-term. The National Canine Cancer Foundation reports that males and German Shepherds are more affected by leukemia than other types of dogs; the average age at diagnosis is 5.5 years old, when most pets are approaching seniority.
Acute leukemia in dogs may show some symptoms, but often the disease goes undetected until it’s too late. Loss of appetite, lethargy, excessive thirst or urination, weight loss, and fatigue are all symptoms of canine leukemia. Swelling of the abdomen and lymph nodes is occasionally reported, although hard to detect by pet parents. To diagnose leukemia in dogs, a bone marrow biopsy and blood work are commonly done.
Acute cases can be treated with aggressive chemotherapy, while observation is often the best course of treatment for chronic leukemia. The prognosis for pets diagnosed with leukemia varies widely, with some research reporting survival rates of anywhere from 120 days to two years. There is no way to prevent a dog from developing leukemia, although maintaining a healthy diet and exercising daily will definitely help keep your pet healthy.
Lymphoma in Dogs
A relatively common type of cancer in dogs, lymphoma is caused by too many lymphoid cells; these include lymphocytes and blood plasma, both crucial to a functioning immune system. The disease originates in the bone marrow, thymus, lymph nodes and spleen, all of which contain or create lymphoid cells. Environmental factors have been thought to play a part, specifically exposure to herbicides, paint, solvents and other industrial chemicals. Middle-aged and senior dogs have the highest risk of acquiring lymphoma, while the following breeds of dog may be more genetically inclined to develop the disease:
- Bull Mastiffs
- Basset Hounds
- Saint Bernards
- Scottish Terriers
- Airedale Terriers
Multicentric lymphoma – originating in multiple places – is the most common type, responsible for roughly 80 percent of canine cases. The primary indicator of this form of cancer is extreme lymph node swelling. Although painless, a dog’s lymph nodes may swell three to ten times larger than normal size; internally, the disease metastasizes to organs. Alimentary lymphoma in dogs is fairly rare, accounting for only 10 percent of cancers, and causing gastrointestinal symptoms. Other, less common forms of lymphoma in dogs include mediastinal and extranodal.
There are five stages of lymphoma, classified by the cancer’s severity and how much it has metastasized. The good news is 90 percent of dogs improve somewhat after treatment, according to Merck Veterinary Manual; the survival rate differs according to the type of cells affected by the lymphoma and how much the cancer has metastasized. Chemotherapy and radiation are the most common courses of treatment for lymphoma in dogs, combined with surgery when possible. No successful preventative measures have been discovered yet, although pet parents may want to avoid using household chemicals like herbicides and outdoor paint around their animals, as these have been linked to lymphoma in dogs and are also toxic.
(Blood Cancer Awareness Month logo courtesy of the Leukemia & Lymphoma Society)