Masses in the spleen occur primarily in middle-aged to older dogs. In many cases, splenic masses consist of only benign hematomas or fibrous nodules.
However, these masses can sometimes be highly malignant forms of cancer, especially a vascular cancer known as hemangiosarcoma.
The spleen is a highly vascular organ that sits in the left, front of the abdomen. It functions as a reservoir of blood and as a filter to remove old blood cells from the circulation. The spleen also contains lymph tissues and can become enlarged in leukemia or lymphoma.
Dogs with tumors of the spleen often develop a bloated or pendulous abdomen as this organ enlarges.
These dogs may otherwise appear normal, or they may develop generalized signs of lethargy and loss of appetite. In some cases, the tumor can bleed into the abdomen (filling the belly with blood), and can even rupture suddenly, leading to rapid internal bleeding, collapse, and shock. Malignant cancers such as hemangiosarcoma can spread to nearby organs such as the liver, so that affected dogs can also develop liver problems. Anemia in dogs is a common finding with hemangiosarcoma, so that dogs become easily tired and develop pale gums.
Your veterinarian may be able to feel a splenic mass by palpating the abdomen.
However, in most cases he or she will want to use abdominal x-rays or ultrasound to pinpoint where the problem lies. In the case of a bleeding tumor, your vet may also want to draw fluid from the abdomen. Blood work may be needed to gauge the degree of anemia and to rule out other problems.
The treatment of choice for splenic tumors is surgical removal of the spleen.
Your vet will want to send a sample of the removed organ for histologic examination, to determine if the tumor is benign or malignant. In the case of benign tumors, surgery is curative and treated dogs usually get along well without a spleen. In the case of malignant tumors, surgery may not slow the spread of the cancer, but it does remove the discomfort caused by the bloated belly, as well as the risk of bleeding. Chemotherapy is not usually an effective treatment for hemangiosarcoma, and dogs with this form of cancer have a poor long-term prognosis.
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