Spleen Tumor in Cats: Symptoms, Types, and Prognosis

Name: Spleen Tumor in Cats: Symptoms, Types, and Prognosis
Creator: Dr. Zubair Khalid

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-10-03

A spleen tumor in cats symptoms often start quietly, with vague signs like hiding, tiredness, or a belly that looks fuller than usual. Some cats have no obvious signs until the mass bleeds, which can cause sudden collapse. The spleen is an organ that filters blood and stores some blood cells, so a growth there can cause problems in several ways at once.

This article is educational and is not a substitute for veterinary diagnosis or treatment.

Quick Answer

A splenic mass in a cat may be benign or malignant, and imaging alone often cannot tell the difference. A tissue sample is usually needed.
Common signs include lethargy, hiding, poor appetite, weight loss, vomiting, a distended abdomen, and pale gums.
Hemangiosarcoma is a rare cancer in cats, but it is one of the malignant tumors that can affect the spleen [1][2].
Splenectomy (surgical removal of the spleen) is the standard first step for most splenic masses, and many cats live well without a spleen.
Sudden weakness, collapse, or a rapidly swelling belly is an emergency and needs immediate veterinary care.

What a Spleen Mass in Cats Actually Means

The spleen sits in the front part of the abdomen, tucked near the stomach and left kidney. It stores red blood cells, removes old ones from circulation, and helps the immune system respond to infection. When a lump grows in the spleen, it can be a harmless overgrowth of normal tissue, a benign tumor, or a cancer.

Veterinarians use the term "splenic mass" or "splenic nodule" because the physical appearance on ultrasound does not confirm what the tissue is. A small, well-defined nodule may look innocent and still turn out to be malignant. In one reported case, a single small splenic nodule was initially thought to represent a benign process, but follow-up imaging showed the mass had grown from 2 cm to 3.5 cm in four weeks, and surgery confirmed hemangiosarcoma [2]. That is why a definitive answer usually comes from a pathologist, not from a picture.

Benign Versus Malignant Tumors

Benign splenic masses in cats include nodular hyperplasia, hematomas, and benign growths of blood vessels or connective tissue. These do not spread to other organs, and removing the spleen is often curative.

Malignant tumors include hemangiosarcoma, lymphoma, mast cell tumors, and other sarcomas. Hemangiosarcoma is a cancer of blood vessel lining cells. It is uncommon in cats compared with dogs, and the veterinary literature on how it behaves in cats is limited [1]. Lymphoma is a cancer of lymphocytes, the white blood cells that help fight infection, and it occurs in middle-aged to older cats [3]. Cats infected with feline leukemia virus or feline immunodeficiency virus have a higher risk of developing lymphoma [3].

Feature	Benign splenic mass	Malignant splenic mass
Spread to other organs	No	Possible
Risk of internal bleeding	Low, but possible	Higher, especially with hemangiosarcoma
Usual treatment	Splenectomy	Splenectomy, sometimes with chemotherapy
Typical outlook	Often good after surgery	Variable, depends on tumor type and stage

Spleen Tumor in Cats Symptoms: What You May Notice at Home

Signs can be subtle for weeks. Many owners describe a cat that is "just not herself." Others notice nothing until the cat collapses.

Early or Vague Signs

Sleeping more and hiding in unusual places
Eating less or skipping meals
Weight loss despite normal eating
Vomiting or diarrhea
A belly that looks rounder or feels firm
Pale gums or inner eyelids

A 14-year-old cat with splenic hemangiosarcoma was brought to an emergency service after a week of lethargy and hiding, and ultrasound found an enlarged spleen with multiple nodules plus fluid in the abdomen that was consistent with bleeding [1]. That timeline is typical. The signs were mild at first, then escalated.

Signs of Bleeding or Advanced Disease

Sudden weakness or collapse
Rapid breathing or panting
A belly that swells quickly
White or very pale gums
Cool limbs

Hemangiosarcoma tumors are fragile and can rupture and bleed into the abdomen. A 15-year-old cat with hemangiosarcoma in the pancreas, a related tumor type, died suddenly at home, and post-mortem examination found a large amount of blood in the abdomen and severe anemia [4]. Sudden death can be the first sign in some cats, which is why any collapse should be treated as an emergency.

Is Spleen Cancer in Cats Painful?

Many cats with a splenic mass do not show obvious pain, which is part of why the disease can go unnoticed. Discomfort, when it happens, tends to come from a stretched abdomen, bleeding, or pressure on nearby organs. Cats are also good at hiding pain, so a cat that seems "fine" may still have a serious problem. If your cat flinches when you touch the belly, breathes fast, or refuses to move normally, that warrants a same-day call to your veterinarian.

Causes and Risk Factors

Most splenic tumors in cats do not have a single known cause. Age is the strongest risk factor. Lymphoma occurs in middle-aged to older cats, and no breed is known to have a higher risk than others [3]. Viral infections with feline leukemia virus and feline immunodeficiency virus raise the risk of lymphoma [3].

Hemangiosarcoma in cats is rare, and researchers are still working out how it behaves [1]. Sun exposure and chronic inflammation are linked to some hemangiosarcomas on the skin and ear, but that does not apply to tumors inside the spleen [5]. There is no evidence that diet, vaccines, or a specific lifestyle causes splenic cancer in cats.

Some cats with a splenic mass also have disease elsewhere. A cat with chronic kidney disease was found to have a splenic mass on ultrasound during the workup for that condition [2]. If your cat has another illness, such as Symptoms Of Kidney Disease In My Cat, your veterinarian may look at the spleen as part of a full abdominal evaluation.

How Veterinarians Diagnose a Splenic Mass

The workup usually happens in stages.

Physical Examination and Blood Work

Your veterinarian will feel the abdomen, check gum color, and listen to the heart and lungs. Blood work shows whether your cat is anemic, which can point to bleeding, and whether other organs are affected. A cat with a splenic mass and new marked anemia is a strong candidate for urgent imaging [2].

Imaging

Abdominal ultrasound is the main tool. It shows the size, number, and texture of splenic nodules and can detect free fluid in the abdomen. Fluid that looks like blood is a red flag for a bleeding tumor [1]. Chest X-rays or a CT scan may be recommended to check for spread.

Sampling the Mass

Ultrasound-guided fine needle aspiration collects cells for review, but it does not always give a clear answer, and it carries a small risk of bleeding from a vascular tumor. Surgical removal of the spleen with full histopathology is the most reliable way to get a diagnosis, and it is often both the diagnostic step and the treatment [2].

If your cat has a lump on the body that needs similar testing, the approach is comparable to what is described in Ear Polyps in Cats: Signs, Diagnosis, Surgery, and Recurrence, where imaging and tissue sampling guide the plan.

Treatment Options for Spleen Cancer in Cats

Surgery

Splenectomy is the standard treatment for a splenic mass. The surgeon removes the spleen through an incision in the abdomen. Cats tolerate life without a spleen well because other organs take over its filtering and storage jobs. In the reported hemangiosarcoma case, the cat underwent a routine splenectomy and recovered enough to start chemotherapy [1]. In another case, a cat was discharged and started on metronomic thalidomide 16 days after surgery [2].

Chemotherapy

Chemotherapy is considered when the tumor is malignant or has spread. One cat with splenic hemangiosarcoma received doxorubicin after surgery, then a combination of cyclophosphamide and vincristine when the disease progressed [1]. Another cat received metronomic thalidomide, which is a daily low-dose drug regimen, after splenectomy [2]. Your veterinarian calculates the dose from your cat's weight and health, and side effects vary.

Supportive Care

Supportive care may include fluids, anti-nausea medication, appetite support, and pain control. If your cat has another condition at the same time, such as Pancreatitis In Cats Symptoms, that condition also needs treatment, because it affects how well your cat handles surgery and recovery.

Recovery, Outlook, and Long-Term Management

Recovery from splenectomy is usually measured in days to a couple of weeks. Most cats go home within a few days of surgery and need rest, a quiet space, and a recheck. The outlook depends almost entirely on what the pathologist finds.

Benign masses generally carry a good prognosis once removed. Malignant tumors are more variable. In one reported case of splenic hemangiosarcoma, the cat survived 205 days from first presentation to euthanasia, with chemotherapy and a second surgery for a metastatic lymph node along the way [1]. In another case, the cat was euthanized 169 days after splenectomy when a liver mass and abdominal fluid were found [2]. These are single cases, not averages, and every cat responds differently.

Long-term management may include periodic ultrasound, blood work, and chemotherapy monitoring. Some cats with cancer in other organs face similar follow-up schedules, which is discussed in Feline Feline Mammary Tumors: Diagnosis and Management. If your cat has a virus that affects the immune system, such as the one behind FIP in Cats: Symptoms, Diagnosis, and How It Is Treated Today, tell your veterinarian, because it can change how the case is managed.

Prevention

There is no proven way to prevent a splenic tumor in a cat. The most useful steps are early detection and routine care.

Keep up with wellness visits, especially after age 8.
Ask your veterinarian to feel the abdomen at every exam.
Report any change in appetite, energy, or belly size right away.
Keep your cat current on testing for feline leukemia virus and feline immunodeficiency virus, since these raise lymphoma risk [3].
If your cat has a known mass, follow the recheck schedule exactly. Growth over a few weeks is meaningful [2].

Limitations and When to Contact a Veterinarian

No article can tell you what your cat's mass is. Only your veterinarian, with an exam and usually a tissue sample, can do that. Use these timing guidelines.

Emergency now: collapse, difficulty breathing, a belly that swells suddenly, white gums, or unresponsiveness.
Same day: pale gums without collapse, sudden weakness, repeated vomiting, or a cat that will not eat or drink.
Routine visit within days: a new firm belly, gradual weight loss, or a mass your veterinarian has been monitoring.

If your cat has any of the emergency signs, go to the nearest emergency hospital. Do not wait for a scheduled appointment.

Frequently Asked Questions

Can a spleen tumor in cats be benign?

Yes. Nodular hyperplasia, hematomas, and some benign growths are common reasons for a splenic mass. The only reliable way to know is to have the tissue examined by a pathologist after removal.

How long can a cat live without a spleen?

Cats generally live normal lives without a spleen. Other organs take over its filtering and blood storage roles, and most cats recover from surgery within a couple of weeks.

Does a splenic mass always need surgery?

Not always. A very small nodule may be monitored with repeat ultrasound if your veterinarian thinks the risk of surgery is high. If the mass grows or your cat develops anemia or bleeding, surgery becomes more urgent.

Can chemotherapy cure spleen cancer in cats?

Chemotherapy is usually used to slow the disease and improve comfort, not to cure it. Some cats tolerate it well, and response varies by tumor type, stage, and the individual cat.

What should I ask my veterinarian after a diagnosis?

Ask what type of tumor it is, whether it has spread, what the surgery involves, what monitoring is planned, and what signs mean you should come back right away. Write the answers down so you can review them later.

References

Novel presentation of a feline patient with visceral and cervical lymph node hemangiosarcoma. Journal of the American Veterinary Medical Association, 2024.
Splenic haemangiosarcoma in a cat treated with splenectomy and metronomic thalidomide. JFMS open reports, 2025.
Immune System Tumors in Cats - Cat Owners. Merck Veterinary Manual.
Hemorrhage and Sudden Death in a Cat with Pancreatic Hemangiosarcoma. Veterinary sciences, 2022.
Total ear canal ablation for the treatment of auricular hemangiosarcoma in a cat: case report. Brazilian journal of veterinary medicine, 2026.