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Splenic Mass in Dogs or Cats

Splenic Mass, Torsion, Thrombosis

The spleen’s function is to filter out old and damaged red blood cells and assist in immune function of the bloodstream. This makes the spleen a very vascular organ, rich with blood vessels. These blood vessels can become damaged or develop cancer which can cause masses to grow on the spleen.

How is a splenic mass diagnosed?

Larger masses of the spleen can sometimes be diagnosed on physical exam and abdominal palpation, however the majority require imaging such as x-rays, ultrasound, or CT scan to determine if the mass is truly associated with the spleen and not another abdominal organ.


If a mass is present, it can be sampled using a fine needle aspirate to try and diagnose the identity of the splenic mass. We typically get a diagnosis about 50% of the time with splenic fine needle aspirates.


Chest x-rays are recommended to look for potential spread of cancer to the heart and lungs. Blood values are also important to evaluate for anemia, signs of infection, and other organ health before undergoing anesthesia and surgery for splenectomy.


Unfortunately, we often cannot determine the exact cause of the splenic mass without removing the spleen and submitting it for histopathologic analysis. Occasionally, the pathologist will require additional special stains to determine the exact cancer type, and the best treatment moving forward.

Splenic Mass Removed

How can a splenic mass be treated?

Splenectomy (removal of the spleen) is the treatment of choice for all splenic masses, regardless of underlying diagnosis. At the time of surgery, additional biopsies will be taken of any other abnormal looking organ tissues. The liver is the most common place to find metastasis (cancer spread) in the abdomen in patients with splenic hemangiosarcoma. Patients diagnosed with benign tumors are cured with splenectomy. Patients diagnosed with malignant tumors will likely benefit from chemotherapy after surgery to prolong survival. Because hemangiosarcoma is the most common diagnosis in dogs with splenic tumors, below is a general summary of survival with different treatment approaches.


  • Splenectomy only - 1-3 month median survival time

  • Splenectomy + Chemotherapy - 3-9 months median survival time

    • Typically a doxorubicin injection once every 2-3 weeks for 6 doses followed by low dose oral chemotherapy.


Dogs with splenic masses undergoing splenectomy are at a higher risk for abnormal heart rhythms (arrhythmias) during and after surgery. We monitor for heart abnormalities using EKG monitors during surgery and for several hours after. Most stable patients that undergo splenectomy recover well and are able to be discharged the same day. Longer hospitalization and blood transfusion may be necessary in dogs that had significant bleeding into the belly or develop arrhythmias. In large breed, deep-chested dogs, we also recommend performing gastropexy at the time of splenectomy to reduce the risk of Gastric Dilatation Volvulus syndrome (GDV, or “Bloat”) in the future.


Pets with splenic masses, may show obvious signs of abdominal distention, or may have less obvious signs such as lethargy, weakness, vomiting, and pale gums. Over time, the diseased spleen can rupture and cause life-threatening bleeding into the abdomen (hemoabdomen) that can lead to death if not addressed quickly. Ideally, the splenic mass is diagnosed and removed before it bleeds into the abdomen. 


Possible causes for a splenic mass include malignant tumors (eg. hemangiosarcoma, lymphoma, histiocytic sarcoma), benign tumors (splenic hemangioma) and splenic hematoma (large internal bleed). Most splenic masses, unfortunately, are malignant tumors. In general, about ⅔ of splenic masses in dogs will be malignant, and ⅓ benign. When the tumor is malignant, the majority are hemangiosarcoma, an aggressive cancer of the blood vessel lining. 

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