The spleen is a flattened, oblong organ that removes pathogens and worn out blood cells from the bloodstream. It is a spongy organ located behind the stomach, just under the diaphragm. The spleen develops masses, benign or malignant, around it intermittently.
Spleen cancer in dogs is either hemangiomas (benign) or hemangiosarcomas (malignant). These arise from the red pulp, which performs most of the functions related to blood cells. The other component, the white pulp, is part of the lymphatic system and functions just like lymph nodes.
Hemangiosarcomas are a common type of dog cancer and occur mostly in the spleen or the heart. It is also the most common cause of abdominal hemorrhages. As both hemangiomas and hemangiosarcomas develop from the blood vessels of the red pulp, it results in the multiplication of uncharacteristic blood vessels. Finally, these abnormal blood vessels burst and the spleen bleeds profusely. The bleeding may stop within a day, but eventually the mass is bound to bleed again.
Excessive bleeding causes extreme weakness and sensitivity to cold. It also changes the color of the gums to a pale shade. If the dog has not lost too much blood and the tumor is benign, surgical excision usually resolves the condition. However, it is better to remove the spleen as soon as the tumor is detected rather than to wait for the bleeding to occur. If the spleen is actively bleeding, you may have to move the dog immediately to an emergency facility and get it removed.
Hemangiosarcomas, being malignant, have to be handled differently. Hemangiosarcomas cause anemia, low platelets and coagulations in the vascular system and an abnormal rate of muscular contractions. Malignant spleen tumors also need to be removed surgically. However, spleen tumors in dogs are highly metastatic and there is a great likelihood that the cancer would have spread widely within the dog’s body.
Almost 66% of spleen cancers in dogs are malignant and two thirds are hemangiosarcomas. Malignant cancer of any type is a potentially fatal condition. Hemangiosarcoma, however, is a bit different from other types of cancers like melanomas and squamous cell carcinoma in dogs. It is a blood-fed sarcoma, which means that the abnormal blood vessels develop within in the tumor and are essentially filled with blood. The most common cause of death is rupturing of the tumor and the dog bleeds to death.