Canine Spleen Cancer
Canine spleen cancer usually occurs in the form of canine hemangiosarcoma, although it can also occur in the form of lymphosarcoma and mast cell tumors. This page looks at the symptoms, causes, and conventional treatment of spleen cancer in dogs.
The spleen is located below the stomach and its main function is to store blood for emergencies and destroy old red blood cells. Although not a vital organ, the spleen is nonetheless important because it forms an important part of the body's immune system.
The spleen has a red soft surface and contains a "red pulp" and a "white pulp". The "red pulp" functions as a filter that removes harmful substances from the blood,
whereas the white pulp helps to fight infections.
Sometimes tumors grow in the spleen. These tumors can either be benign (hemangiomas) or malignant. For malignant tumors, they can either be
which grow from the red pulp, or mast cell tumors and
that grow from the white pulp.
In dogs, most splenic tumors are either hemangiomas or hemangiosarcomas. Hemangiosarcoma represents about 45-51% of canine spleen cancer.
What is Canine Hemangiosarcoma?
Hemangiosarcoma is a soft tissue sarcoma cancer that arises out of blood vessels - the arteries or veins. Since they come from the walls of blood vessels, they are usually filled with blood. Canine hemangiosarcoma can arise as a single tumor or multiple tumors. The tumor can get very large, especially in the spleen. Eventually the tumor ruptures and bleeds, resulting in life-threatening blood loss.
Hemangiosarcomas have a fairly high rate of metastasis. By the time the tumors are first diagnosed, they will most likely have already spread to other sites of the body. The most frequent organs to which hemangiosarcomas metastasize are the liver and lungs, but they can also spread to the kidneys, muscle, lymph nodes, adrenal glands, and brain.
Some breeds of dogs are more prone to hemangiosarcomas, such as the Golden Retrievers, Labs, and German Shepherds. The average age of affected dogs is 8 to 10 years. Males are more susceptible to this form of cancer than females. There is also now evidence that spaying and neutering increases the risk of hemangiosarcoma.
Symptoms of Canine Spleen Cancer
Canine hemangiosarcoma in the spleen sometimes causes weakness, especially in the hind legs, and decreased energy that lasts for a day or two, then goes away only to reappear weeks or months later. The reason for this waxing and waning condition is due to the bleeding of the tumor. When the tumor bleeds, the blood goes in and around the tumor, which causes weakness in the dog. The gums turn pale or white (due to anemia
). The dog may lose his appetite. Then in a day or two, the blood goes back into the circulation causing the dog to feel better. This is called "autotransfusing", which is the body's way of recovering blood within the abdomen.
In some cases, however, the blood loss is very rapid and the signs can deteriorate. Eventually, the dog will bleed to death.
Diagnosis and Treatment of Canine Spleen Cancer
The tests used to diagnose hemangiosarcomas include:
- Blood and serum biochemistry tests
- Blood clotting test
- Abdominal ultrasound
However, biopsy is the only way to obtain a definitive diagnosis.
Surgery is the conventional treatment of choice for canine hemangiosarcoma in the spleen. The spleen is either partially or completely removed. However, less than 10% of the dogs survive more than a year after surgery.
Chemotherapy with doxorubicin after spleen removal increases survival times to about 4.5 to 6 months.
Radiation therapy is rarely used for canine spleen cancer due to its proximity to other vital organs.
Recent research at the University of Wisconsin Veterinary School has found that using the chemotherapy drugs doxorubicin and cyclophosphamide along with an immune
stimulant called liposome-encapsulated MTP-PE (L-MTP-PE, or liposome-encapsulated muramyl tripeptide phosphatidylethanolamine) increased survival time to about 9 months. However, more tests need to be done to confirm efficacy of this therapy protocol.