Splenic Tumors In Dogs And Cats

A Guide for Pet Owners

What Is the Spleen and What Does It Do?

The spleen is a soft, elongated organ that sits in the abdomen near the stomach. In dogs and cats it has several important jobs: it filters and stores blood, removes old or damaged blood cells, and helps the immune system respond to infection. Because the spleen is rich in blood vessels and blood filled tissue, it is also a common site for tumors, especially in older dogs.

A splenic tumor is an abnormal growth of tissue within or on the spleen. Some of these growths are benign, meaning they do not spread to other organs, while others are malignant, meaning they can invade nearby tissue or spread through the bloodstream to distant sites such as the liver, lungs, or heart.

Common Types of Splenic Tumors

In Dogs

Dogs are affected by splenic tumors more often than cats, and large breed, middle aged to older dogs are at the highest risk. Common types include:

Hemangiosarcoma: a fast growing, malignant tumor of the blood vessel lining. It is the most frequent cause of splenic masses in dogs and is unfortunately aggressive, often spreading before it is found.
Hemangioma: a benign counterpart to hemangiosarcoma, made of abnormal but noncancerous blood vessel tissue.
Splenic hematoma: not a true tumor but a blood filled swelling that can look similar on imaging.
Other sarcomas, lymphoma, and histiocytic tumors, which occur less frequently.

Breeds such as German Shepherds, Golden Retrievers, and Labrador Retrievers appear to have a higher predisposition to hemangiosarcoma, though any breed can be affected.

In Cats

Splenic tumors are less common in cats than in dogs, but when they occur, lymphoma is the most frequently diagnosed type. Mast cell tumors and hemangiosarcoma can also affect the feline spleen, though these are rarer. Older cats are more likely to be diagnosed.

Signs and Symptoms to Watch For

Splenic tumors can grow silently for a long time before causing noticeable symptoms. In many cases, the first sign is sudden collapse or weakness caused by internal bleeding when a fragile tumor ruptures. Other signs pet owners may notice include:

A swollen or distended abdomen
Pale gums
Lethargy or reduced interest in activity
Decreased appetite or weight loss
Episodes of weakness that come and go
Rapid breathing or an increased heart rate
In severe cases, sudden collapse, which is considered an emergency. This is usually due to the splenic tumor rupturing causing internal bleeding in to the abdomen.

Because these signs can also point to many other conditions, any dog or cat showing them should be examined by a veterinarian promptly.

How Splenic Tumors Are Diagnosed

Veterinarians typically use a combination of the following tools to identify and evaluate a splenic mass:

Physical examination, including feeling the abdomen for an enlarged spleen
Blood tests to check for anemia, abnormal cell counts, or clotting problems
Abdominal ultrasound to visualize the spleen, measure the mass, and look for fluid or spread to other organs
Chest X rays to screen for spread to the lungs
Fine needle aspiration or biopsy, when safe to perform, to identify the tumor type under a microscope
Advanced imaging such as CT scans in some referral or specialty settings

Because many splenic masses bleed easily, veterinarians are often cautious about needle sampling and may instead recommend surgery to both diagnose and treat the mass at the same time.

Treatment Options

Surgery

The most common treatment for a splenic tumor is splenectomy, or surgical removal of the spleen. Dogs and cats can live a full and active life without a spleen, since other organs such as the liver take over most of its functions. Surgery is often recommended urgently if the tumor has ruptured and is causing internal bleeding.

Chemotherapy

If the tumor is found to be malignant, particularly hemangiosarcoma or lymphoma, chemotherapy may be recommended after surgery to slow the spread of cancer cells and extend quality time. A veterinary oncologist can discuss the specific protocol, likely side effects, and expected benefit for the individual pet.

Supportive and Palliative Care

For pets who are not good candidates for surgery, or for families who choose not to pursue aggressive treatment, supportive care can help maintain comfort. This may include pain control, monitoring for internal bleeding, dietary support, and regular check ins with the veterinary team.

Prognosis

Prognosis varies widely depending on the tumor type, its size, whether it has spread, and how quickly it is caught.

Benign tumors such as hemangioma generally carry an excellent outlook once removed.
Malignant tumors such as hemangiosarcoma are more serious. Without treatment, survival is often measured in weeks. With surgery alone, many dogs live a few months. With surgery plus chemotherapy, some dogs gain additional months, and a smaller number live considerably longer. In my experience the spread to the lungs becomes evident around six months after surgery. But typically this has been good quality of life for the six months.
Feline lymphoma of the spleen can sometimes respond well to chemotherapy, with many cats achieving periods of remission.

Every pet is different, and a veterinary oncologist can offer the most accurate outlook based on the specific diagnosis, staging results, and the pet’s overall health.

Caring for a Pet With a Splenic Tumor

Follow all post surgical instructions closely, including activity restriction while incisions heal.
Watch for signs of internal bleeding, such as pale gums, weakness, or a swollen belly, and seek emergency care right away if these appear.
Keep all follow up appointments for bloodwork and imaging to monitor for recurrence or spread.
Ask your veterinary team about nutrition, since a balanced diet supports recovery and overall wellness.
Consider a consultation with a veterinary oncologist for guidance on chemotherapy options and expected outcomes.
Reach out for emotional support if needed. Caring for a pet through a cancer diagnosis can be difficult, and many veterinary hospitals can point you toward resources for pet loss and caregiver support.

When to Seek Emergency Care

A ruptured splenic tumor can cause life threatening internal bleeding within a short period of time. If a dog or cat suddenly collapses, has pale or white gums, seems disoriented, or has a rapidly swelling abdomen, this is an emergency. Go to the nearest veterinary emergency hospital immediately rather than waiting for a routine appointment.

Key Takeaways

The spleen is a blood filled organ that is a common site for tumors in older pets, especially large breed dogs.
Tumors can be benign or malignant, with hemangiosarcoma being the most concerning type in dogs.
Symptoms are often subtle until a tumor ruptures, so regular veterinary checkups matter.
Diagnosis relies on imaging, bloodwork, and often surgery.
Surgical removal of the spleen is usually the primary treatment, sometimes followed by chemotherapy.
Prognosis depends heavily on tumor type, so a clear diagnosis is essential for planning care.

This article is for general educational purposes and is not a substitute for advice from your veterinarian, who knows your pet’s individual health history.