Canine Splenic Tumors - What You Need To Know

Canine splenic tumors (tumors of the spleen) can be challenging. We either find them incidentally while performing imaging of the abdomen (x-rays or ultrasound) or we discover them after they have ruptured.

In the second scenario, a large splenic mass ruptures, causing the patient to feel weak, lethargic or even collapse. Sometimes there is a history of the patient having a few weeks of waxing and waning lethargy and decreased appetite; this is a result of the mass having small bleeds (instead of one large rupture) over a period of time.

The rupture of a splenic mass can be life-threatening. This is because a large volume pools into the abdomen and there isn't enough left for the heart to pump throughout the body to sustain the organs; often the patient comes to the ER in some degree of shock and is in need of blood transfusion, IV fluids, monitoring for heart arrhythmias, and removal of the bleeding spleen.

Deciding whether to pursue surgery in this situation can be a very difficult decision. Families are faced with knowing that they need to immediately decide whether to hospitalize their dog and perform emergency surgery to remove his spleen and give him a blood transfusion. A complicating factor is not knowing whether the mass in the spleen is benign (meaning that their dog will be cured with surgery) or malignant (their dog is likely to have a relatively short survival after surgery).

The Statistics...

We wish we knew which of these tumors were benign and which were malignant ahead of time. When we find a mass in the spleen that hasn't ruptured, in some cases it's safe to sample and try to obtain a diagnosis.

If the tumor is "cavitated" or blood-filled, sampling the mass would risk rupturing the tumor, which is never advised. The general recommendation for any mass in the spleen is to remove the spleen because both benign and malignant tumors can rupture (which we never want).

When talking about canine splenic masses, we have traditionally referred to the "double two-thirds" rule. This means that approximately two-thirds of dogs with a splenic mass will have a malignant tumor (cancer that can spread to other organs) and two-thirds of those malignant tumors will be hemangiosarcoma (an aggressive cancer of abnormal blood vessels).

Other studies have shown that 63-70% of dogs that develop a hemoabdomen (free blood in the abdomen) from a ruptured splenic tumor had hemangiosarcoma. In these cases, the tumor is more likely to be hemangiosarcoma, but some people get lucky and their dog has a benign tumor.

It seems that dogs that have splenic tumors that are found incidentally and have not ruptured are more likely to be benign (70%) than malignant. In this study, of the 30% of tumors that were malignant, the majority were hemangiosarcoma (58%). The median life expectancy (half lived longer, half lived shorter) of dogs with hemangiosarcoma is 4.4 - 6.5 months (depending on the study). In these studies, many patients did not receive chemotherapy (which might have helped them live longer).

Dogs that have stage I hemangiosarcoma, like these patients (non-ruptured) and have surgery, typically live at least twice as long as patients that are diagnosed after their tumor as ruptured. Patients with stage II disease (ruptured tumor) that have surgery but do not receive chemotherapy, live approximately two and a half months (although this is variable). If they have surgery and chemotherapy, the average survival is 4-6 months (so the stage I patients do quite a bit better than stage II).


Traditional chemotherapy for hemangiosarcoma consists of six doses of doxorubicin chemotherapy. Many oncologists will place their patients on a metronomic chemotherapy protocol after traditional chemotherapy is finished (metronomic = low dose oral chemo).

Recently, there has been very preliminary evidence that certain Chinese herbs and other therapies may be helpful for hemangiosarcoma patients, so it's not uncommon for some oncologists to combine Yunnan Baiyao and propranolol with traditional chemotherapy.

*Please note that although Im-Yunity (coriolis versicolor mushroom) was previously shown to improve survival in a UPenn study, a more recent (larger) study (also UPenn) showed that it did not help. A current trial is evaluating whether a combination of Chinese herbs can give these patients a survival advantage; this study is being conducted at five private practice locations across the US.

There is some evidence that small breed dogs are less likely to have malignant tumors of the spleen, and of those tumors that are malignant, fewer are hemangiosarcoma than in large breed dogs. Another study showed similar evidence - dogs weighing less than 27.5 kg (61 pounds) were significantly less likely to be diagnosed with hemangiosarcoma) than dogs weighing greater than 27.5 kg.

How to ensure the best outcome

Want the best outcome? Have the splenectomy performed by a doctor that has done a TON of these in a clinic with 24-hour care and monitoring, with the ability to administer a blood transfusion, and monitor for arrhythmias.

Prior to surgery, it is ideal ensure that there is no obvious evidence of cancer spread (metastasis). If metastasis has occurred, patients will not live as long as the averages quoted above.

Appropriate staging for a patient that has a hemoabdomen (free blood in the abdomen) due to a ruptured splenic tumor or a non-ruptured splenic mass typically involves:

(1) 3-view chest x-rays reviewed by a radiologist - this is done to ensure that the lungs are free of obvious cancer

(2) Abdominal ultrasound - this is done to ensure that there doesn't appear to be obvious evidence of cancer in multiple organs

(3) Assess the heart for the presence of a right auricular/right atrial mass using ultrasound - some dogs with splenic hemangiosarcoma will also have hemangiosarcoma affecting the heart, which typically worsens prognosis

Hemangiosarcoma is most common in golden retrievers and German shepherds, but any breed can be affected by a benign or malignant tumor in the spleen.

If your dog becomes lethargic, develops a decreased appetite, displays a waxing and waning weakness, or is "just not himself", have your vet perform an exam and diagnostic tests if indicated. It could just be "old age" but if it isn't, it's better to make a diagnosis sooner than later, because an early diagnosis typically leads to a better prognosis.

Dr. Lori Cesario

Board Certified Veterinary Oncologist

PS: I'm happy to now offer online oncology consultations. Learn more about how this service can help by visiting the Vet Cancer Consultants site.

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