Hemangiosarcoma in Cats: Symptoms, Treatment, and Prognosis

Name: Hemangiosarcoma in Cats: Symptoms, Treatment, and Prognosis
Creator: Dr. Zubair Khalid

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-10-02

Hemangiosarcoma in cats is a rare cancer that starts in the cells lining blood vessels. It usually appears either as tumors in or under the skin or as tumors inside the body, most often in the spleen, heart, or liver. Because the feline form is uncommon and behaves differently from the disease in dogs, owners often hear conflicting information. This article is educational and is not a substitute for veterinary diagnosis or treatment.

Quick Answer

Hemangiosarcoma in cats is rare, and the skin and subcutaneous forms are seen more often than the internal (visceral) forms [1].
Sun exposure plays a role in many skin cases, especially on the head, ears, and other lightly pigmented areas [1].
Diagnosis almost always requires a tissue sample (biopsy) because blood tests and imaging cannot confirm the tumor type on their own.
Surgery is the main treatment when the tumor can be removed, and chemotherapy or radiation may be added in some cases [2].
Survival varies widely. Some cats with skin tumors do well for a year or longer, while internal disease is often advanced by the time it is found.

What Is Hemangiosarcoma in Cats?

Hemangiosarcoma is a malignant tumor of endothelial cells, the cells that line blood vessels [3]. Because these cells are found throughout the body, the cancer can arise almost anywhere. In cats, the two broad groups are cutaneous (skin) hemangiosarcoma and visceral (internal) hemangiosarcoma.

The skin form includes tumors in the dermis and the tissue just under the skin. These are the most common type in cats and are often linked to chronic ultraviolet radiation exposure [1]. They tend to show up on areas with less pigment and less hair, such as the ears, the nose, and the eyelids.

The visceral form grows inside the body. Reported sites in cats include the spleen, the pericardium (the sac around the heart), the liver, and the omentum [4][5][6]. These tumors can bleed, which is what makes them dangerous. A related group of tumors called angiosarcomas has a predilection for the ventral abdominal wall in cats, and some of these are true hemangiosarcomas while others arise from lymph vessels [3].

One important point for owners: hemangiosarcoma in cats does not behave like the aggressive, fast-spreading disease seen in many dogs. Cats often have slower-growing tumors, and the skin form in particular can be managed for a long time.

Symptoms of Hemangiosarcoma in Cats

Signs depend on where the tumor is growing. Many cats with skin tumors have no other symptoms at all.

Skin and Subcutaneous Signs

A visible lump or nodule in or under the skin, often dark red or purple
A sore that bleeds, oozes, or will not heal
Redness, flakiness, or ulceration of the skin, especially near the lips or footpads, which can also occur with other skin tumors [7]
A mass on the ear, nose, or eyelid, sometimes with a history of sun exposure [1][8]
Itching or discomfort at the site

Internal (Visceral) Signs

Lethargy and hiding, which are often the first things owners notice [4]
Poor appetite, weight loss, or vomiting
A swollen or painful abdomen from fluid or an enlarged organ
Fast or labored breathing, which can signal fluid around the heart or lungs [5]
Pale gums or weakness from internal bleeding
Neurologic signs if a tumor presses on nerves. One reported cat developed head tilt, nystagmus, and balance problems from a subcutaneous tumor [1]

Because these signs overlap with many other illnesses, including feline hyperthyroidism and other cancers, only testing can sort out the cause.

Causes and Risk Factors

We do not know exactly why any single cat develops hemangiosarcoma, but several factors raise the odds.

Ultraviolet light exposure. Chronic sun exposure is associated with the skin and subcutaneous forms, and tumors often form on the head and other sun-exposed areas [1]. Light-coated, unpigmented cats are at higher risk for ear tumors [9].
Chronic inflammation or trauma. Ongoing ear infections and repeated scratching have been linked to tumors of the ear in cats [9].
Viral status. One reported cat with a subcutaneous hemangiosarcoma tested positive for feline leukemia virus and feline immunodeficiency virus [1]. This does not prove the viruses caused the tumor, but retrovirus testing is reasonable in any cat with an unusual cancer.
Age. Many reported cases involve middle-aged to older cats, though tumors have been described in cats as young as 2 years old [1].
Genetics and environment. Chemical carcinogens, solar radiation, and viruses can all contribute to skin tumors in cats, and hormonal and genetic factors may play a role as well [2].

How Hemangiosarcoma in Cats Is Diagnosed

Your veterinarian will start with a full physical exam and a detailed history. From there, the workup usually follows these steps.

Blood Work and Urinalysis

Blood tests help assess your cat's overall health and can reveal anemia from bleeding, organ changes, or other problems. They cannot confirm hemangiosarcoma. In one reported case, blood counts and chemistry were completely normal despite an advanced tumor [1].

Imaging

Abdominal ultrasound can show masses in the spleen, liver, or omentum and can detect free fluid in the belly [4][6].
Chest X-rays help look for spread to the lungs and for fluid.
Echocardiography is used when the heart or pericardium is involved. In one cat, ultrasound revealed an irregular mass expanding from the pericardium and surrounding the heart [5].

Biopsy and Histopathology

A tissue sample is the only way to confirm the diagnosis. Your veterinarian may take a sample with a needle or remove the mass entirely and send it to a laboratory. In the spleen case described above, histopathology of the removed spleen confirmed visceral hemangiosarcoma [4].

Immunohistochemistry

Sometimes standard histopathology is not enough. A technique called immunohistochemistry uses antibodies to identify the cell of origin. In a series of nine cats with abdominal wall angiosarcomas, immunohistochemistry reclassified two tumors that had been called lymphangiosarcoma as hemangiosarcoma [3]. This matters because it affects treatment and prognosis.

Staging

Staging means checking whether the cancer has spread. It typically includes imaging of the chest and abdomen plus evaluation of nearby lymph nodes. In the nine-cat series, pulmonary metastases were suspected in one cat but were not confirmed with a biopsy [3].

Test	What It Shows	Can It Confirm Hemangiosarcoma?
Physical exam	Lumps, sores, organ enlargement	No
Blood work	Anemia, organ changes, overall health	No
Abdominal ultrasound	Organ masses, free fluid	No, but it guides biopsy
Chest X-rays	Lung spread, pleural fluid	No
Echocardiography	Heart and pericardial masses	No
Biopsy with histopathology	Tumor type and grade	Yes
Immunohistochemistry	Cell of origin (blood vs lymph vessel)	Yes, refines the diagnosis

Treatment Options

Treatment depends on the location of the tumor, whether it has spread, and your cat's overall health. There is no single standard protocol for feline hemangiosarcoma because the disease is so uncommon [4].

Surgery

Surgical removal is the most effective, least costly option with the fewest side effects for most skin tumors [2]. When malignancy is suspected, the surgeon removes the tumor plus a margin of surrounding tissue [2]. For tumors that cannot be removed completely, partial removal may still prolong life [2].

Surgery is also used for internal tumors. Splenectomy is a common approach for splenic hemangiosarcoma, and one reported cat underwent a routine splenectomy followed by chemotherapy [4]. In another case, a cat with a splenic mass had the spleen removed and then received metronomic thalidomide [6]. For tumors of the ear canal, a procedure called total ear canal ablation combined with cryotherapy of the surgical bed was used to maximize the chance of no recurrence, and that cat remained free of recurrence one year later [9].

Chemotherapy

Chemotherapy may be recommended after surgery or when surgery is not possible [2]. One cat with visceral hemangiosarcoma was started on doxorubicin after splenectomy, and when the disease progressed, the plan changed to a combination of cyclophosphamide and vincristine [4]. Another cat received metronomic thalidomide, which is given as a daily low dose instead of in cycles [6].

If your cat is prescribed chemotherapy, your veterinarian will calculate the dose from your cat's weight and health. Side effects can include vomiting, diarrhea, lack of appetite, and fever. Hair loss does not occur in cats receiving chemotherapy [7].

Radiation Therapy

Radiation can be used when a tumor cannot be fully removed or when surgery is not an option [2]. One cat with hemangiosarcoma of the nasal planum was treated with palliative radiation alone, and that cat was still being followed 311 days after treatment [8]. Four other cats in that report had surgery plus strontium-90 therapy [8].

Supportive Care

Some cats need fluid drainage, pain control, appetite support, or treatment for anemia. These measures do not cure the cancer, but they can improve comfort.

Recovery, Outlook, and Long-Term Management

This is the part owners ask about most, and the honest answer is that the outlook varies a great deal.

For skin tumors that are removed with clean margins, many cats do well. In the ear canal case, the cat was free of recurrence one year after surgery [9]. In the nasal planum series, several cats treated with surgery plus strontium-90 were still alive at the time of writing [8].

For internal disease, the picture is more serious. One cat with splenic and lymph node hemangiosarcoma survived 205 days from the first visit to euthanasia, a period that included splenectomy, doxorubicin, combination chemotherapy, and removal of a metastatic lymph node [4]. Another cat with splenic hemangiosarcoma was euthanized 169 days after splenectomy when a liver mass and free abdominal fluid were found [6].

A few points help frame these numbers. First, they come from individual case reports, so they describe what happened to one cat, not what will happen to yours. Second, cats with visceral hemangiosarcoma are often diagnosed late, after the tumor has already bled or spread. Third, quality of life matters as much as length of life. If your cat is eating, interacting, and comfortable, treatment may be worth continuing. If your cat is hiding, vomiting, struggling to breathe, or in pain that cannot be controlled, it may be time to talk with your veterinarian about euthanasia.

Long-term management usually involves regular rechecks with physical exams and imaging to watch for recurrence or new tumors. Keep a simple log of your cat's appetite, energy, and behavior. That record helps your veterinarian adjust the plan.

If your cat has other chronic conditions, such as chronic kidney disease or an overactive thyroid, those need to be managed alongside the cancer. Cats with heart or clotting problems, including aortic thromboembolism, may not tolerate certain treatments.

Prevention

You cannot prevent every cancer, but you can lower some risks.

Limit sun exposure. Keep light-colored cats indoors during peak sun hours and ask your veterinarian about pet-safe sunscreen on the ear tips and nose.
Check the skin monthly. Run your hands over your cat's body, including the ears, belly, and legs. Report any new lump, sore, or non-healing wound.
Treat chronic ear disease. Ongoing inflammation and scratching have been linked to ear tumors in cats [9].
Test for retroviruses. Knowing your cat's FeLV and FIV status helps your veterinarian interpret unusual findings [1].
Keep routine wellness visits. Early detection gives you more options.

Limitations and When to Contact a Veterinarian

No article can tell you what is happening with your individual cat. Every case needs a veterinarian who can examine your cat, review the test results, and tailor a plan.

Contact your veterinarian the same day if you notice a new lump that is growing quickly, a sore that bleeds or will not heal, or a sudden drop in appetite or energy.

Go to an emergency clinic now if your cat has trouble breathing, pale or white gums, a distended belly, collapse, or weakness that comes on suddenly. These can signal internal bleeding or fluid around the heart, which are emergencies [4][5].

Schedule a routine visit if you find a small, stable lump or if your cat has a history of sun exposure and you want a baseline skin check.

Frequently Asked Questions

Is hemangiosarcoma in cats the same as in dogs?

No. The feline form is much less common and generally behaves less aggressively than the canine form. Skin and subcutaneous tumors are seen more often in cats than tumors inside the body [1].

Can hemangiosarcoma in cats be cured?

Sometimes, yes. Skin tumors removed completely with clean margins may not come back, and one cat with an ear tumor remained free of recurrence a year after surgery [9]. Internal tumors are harder to cure because they are often found after they have spread.

How long can a cat live with hemangiosarcoma?

It depends on the location and stage. Reported survival times range from a few months for advanced internal disease to more than a year for some skin tumors [4][8][9]. Your veterinarian can give you a more specific estimate after staging.

Does chemotherapy make cats lose their hair?

No. Hair loss from chemotherapy does not occur in cats, though other side effects such as vomiting, diarrhea, poor appetite, and fever can happen [7].

Should I put my cat through treatment?

That is a personal decision, and your veterinarian can help you weigh it. Ask about the expected benefit, the number of visits, the side effects, and what a good day looks like for your cat. If treatment cannot keep your cat comfortable, humane euthanasia is a valid and caring choice.

References

Vestibular syndrome associated with subcutaneous hemangiosarcoma in a cat. Topics in companion animal medicine, 2026.
Tumors of the Skin in Cats - Cat Owners. Merck Veterinary Manual.
Feline ventral abdominal wall angiosarcoma: haemangiosarcoma or lymphangiosarcoma? Clinical and pathological characteristics in nine cases. Journal of feline medicine and surgery, 2024.
Novel presentation of a feline patient with visceral and cervical lymph node hemangiosarcoma. Journal of the American Veterinary Medical Association, 2024.
Pericardial hemangiosarcoma in a cat. JFMS open reports, 2026.
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.
Hemangiosarcoma of the nasal planum in cats: five cases (2010-2021). Journal of feline medicine and surgery, 2022.
Total ear canal ablation for the treatment of auricular hemangiosarcoma in a cat: case report. Brazilian journal of veterinary medicine, 2026.