Updated September 25, 2026. Fact-checked against veterinary sources; review by a licensed veterinarian is in progress. See our editorial policy.
Quick answer: Spleen masses are common in older, larger dogs. Some are benign, such as hematomas or nodular hyperplasia, but many are malignant, most often hemangiosarcoma, an aggressive cancer of blood vessel cells. Spleen tumors can bleed suddenly into the belly, causing weakness, pale gums, a swollen abdomen, or collapse. That’s an emergency. Treatment usually starts with surgical removal of the spleen (splenectomy), which confirms the diagnosis. Dogs live normally without a spleen.
Signs
- Sudden weakness or collapse, sometimes with recovery hours later (from a small bleed that stops)
- Pale gums
- A swollen belly
- Fast breathing or a fast heart rate
- Lethargy, poor appetite, or weight loss
- Many spleen masses cause no signs and are found on a routine exam or imaging
Emergency signs
Go to an emergency vet immediately for collapse, pale or white gums, a rapidly swelling belly, or labored breathing. Internal bleeding can be life-threatening.
Types of spleen masses
- Hemangiosarcoma: malignant and often has already spread by the time it’s found, commonly to the liver, lungs, or heart.
- Hematoma: a benign blood-filled mass.
- Nodular hyperplasia: benign overgrowth of normal tissue.
- Other cancers, such as lymphoma, other sarcomas, or mast cell tumors.
Studies of dogs with bleeding spleen masses have found that a majority are malignant, most often hemangiosarcoma, but many dogs do have benign masses, so testing matters.
Diagnosis
- Blood count and clotting tests
- Abdominal ultrasound to look at the spleen and liver
- Chest X-rays or CT to look for spread
- Heart ultrasound in some cases, since hemangiosarcoma can involve the heart
- Examination of the removed spleen (histopathology) for a definite diagnosis
Treatment
- Stabilization for bleeding dogs: IV fluids and often blood transfusions.
- Splenectomy: removing the whole spleen. For benign masses, this is usually curative.
- Chemotherapy after surgery for hemangiosarcoma, which can extend survival.
- Heart rhythm monitoring after surgery, as irregular heartbeats are common for a day or two.
Outlook
Dogs with benign masses usually do very well after splenectomy. For hemangiosarcoma, the outlook is guarded: survival with surgery alone is often measured in weeks to a few months, and chemotherapy typically extends this by a few months. A veterinary oncologist can discuss options, including palliative care.
Supplements
Some supplements, such as a medicinal mushroom extract (polysaccharopeptide) and the Chinese herbal product Yunnan Baiyao, are used by some owners and vets. Evidence is limited and mixed. Discuss them with your vet before use, especially around surgery or chemotherapy.
Recovery after splenectomy
- Leash walks only and restricted activity for about 2 weeks
- A cone to protect the incision
- Pain medication as prescribed
- Daily incision checks
- Call your vet for weakness, pale gums, a swollen belly, or trouble breathing
What to avoid
- Human pain relievers, which can cause bleeding and other harm.
- Waiting after a collapse, even if your dog seems to recover.
- Unproven cancer “cures” in place of treatment.
Frequently asked questions
Can a dog live without a spleen?
Yes. Other organs take over its functions, and dogs live normal lives afterward.
Are spleen tumors always cancer?
No. Many are benign. Only examination of the removed tissue can tell for sure.
Is hemangiosarcoma painful?
The tumor itself often isn’t, but bleeding and spread can make dogs weak and uncomfortable. Palliative care focuses on comfort.
Sources
- Merck Veterinary Manual: Hemangiosarcoma in dogs
- Hammond TN, Pesillo-Crosby SA. Prevalence of hemangiosarcoma in anemic dogs with a splenic mass and hemoperitoneum requiring a transfusion: 71 cases (2003–2005). JAVMA. 2008
- Brown DC, Reetz J. Single agent polysaccharopeptide delays metastases and improves survival in naturally occurring hemangiosarcoma. Evid Based Complement Alternat Med. 2012
- American College of Veterinary Surgeons (ACVS): Splenic masses
This article is for general education and is not a substitute for care from your own veterinarian. Learn about The Pet Vet and our editorial policy.