Is That Lump a Sarcoma? How to Identify Warning Signs in Your Cat

What is Sarcoma in Cats?

Sarcoma is a type of cancer that arises from connective tissues like fat, muscle, nerves, and blood vessels in cats. Unlike carcinomas which start in epithelial tissues, sarcomas originate in mesenchymal cells found in supportive and connective tissues (1).

Sarcomas are relatively common in cats, accounting for up to 20% of skin and subcutaneous tumors. The most prevalent forms are fibrosarcomas and liposarcomas. Other types include peripheral nerve sheath tumors, rhabdomyosarcomas, osteosarcomas, chondrosarcomas, hemangiosarcomas, and histiocytic sarcomas (2).

Sarcomas often start small and grow rapidly into large masses under the skin or around joints and bones. They are locally invasive tumors that frequently recur after surgical removal. Lungs, regional lymph nodes, and other organs are also at risk for metastasis or spreading. Prognosis depends on the type, grade, and stage of sarcoma (3).

While the exact causes are unknown, injection sites, trauma, chronic inflammation, and genetic factors may trigger sarcoma development. Some breeds like Siamese cats are predisposed. Since sarcomas are so aggressive, early detection and treatment is key for cats.


Common Signs of Sarcoma in Cats

One of the most common signs of sarcoma in cats is the development of lumps or bumps on the body. These masses may appear on the limbs, abdomen, head, or other parts of the body. According to, “A lump or mass [is] typically slow growing.” These lumps are often firm or solid feeling. The mass may start small but tend to grow larger over time as the cancer spreads.

Cats with sarcoma may develop masses under the skin that feel like bumps or lumps when petting them. These lumps can vary in size and may appear raised above the skin. There may be just one lump or multiple lumps that appear. Though the lumps tend to grow slowly at first, they can grow aggressively as the cancer advances. Monitoring lumps and having any new ones checked promptly is important for cats.


How Sarcoma Lumps Feel on Cats

Sarcoma lumps often present as firm, immobile masses that feel like they are deeply embedded in the tissue underneath the skin. According to, “Soft tissue sarcomas are typically painless.” This is because they do not have many nerve endings. However, some sarcomas that develop in the myelin sheath around nerves can be painful, though this is rare.

The Spruce Pets notes that a fibrosarcoma lump specifically will have a firm, almost rubbery texture, and feel firmly fixed to the tissue below the skin surface. The mass itself is not likely to be painful for the cat, though it can become tender, swollen and infected if the skin over it breaks down.

Sarcoma lumps tend to feel like solid masses adhered deep in the tissue, versus benign lipomas which feel more like fluid-filled sacs under the skin that are mobile when prodded. Checking for mobility vs. deep attachment is one way to distinguish a potential sarcoma from a benign mass. However, the only way to confirm is through veterinary tests.


Sarcoma Lump Locations on Cats

Sarcomas can develop in many locations on a cat’s body, but there are some common areas where they tend to occur:

Limbs: One of the most frequent sites for sarcoma lumps is on the legs and paws. The thighs, ankles, and feet often develop these tumors.

Head: Sarcomas may emerge on a cat’s head, face, and neck region. The mouth, nose, and ears are vulnerable areas.

Abdomen: Abdominal sarcomas can grow on organs like the spleen, liver, and intestines inside the belly.

Chest: The chest cavity contains vital organs, so sarcomas in the chest are serious. They may press on the lungs, heart, and major blood vessels.

In some cases, sarcoma lumps can spread to other parts of the body from the original tumor site. Lungs and lymph nodes are common sites of metastasis.1

Knowing the common locations for sarcoma development can help cat owners identify potential tumors early on. Catching them soon improves treatment success.

When to See the Vet

If you notice any new lumps or bumps on your cat, it’s important to have your veterinarian examine them as soon as possible. Even if the lump seems small or harmless, it could potentially be cancerous. Sarcomas tend to grow quickly, so early detection and treatment is key.

You should also have your vet assess the lump if an existing one changes in any way. Changes to watch for include:

  • The lump rapidly increases in size
  • The lump changes shape or texture
  • The lump becomes painful, swollen, or inflamed
  • The lump starts bleeding or oozing

Even subtle changes in an existing lump warrant a recheck by your veterinarian. Catching sarcoma early when surgical removal has the best prognosis is crucial. According to the American Veterinary Medical Association (AVMA), untreated sarcomas in cats can grow to the size of a grapefruit in just 2-3 weeks.

You should also have any lump on your cat assessed if it’s impairing your cat’s mobility or quality of life in any way. Lumps in areas that receive repeated trauma from daily activity may require removal. Your vet can advise you on the best course of action for your individual cat.

Sarcoma Diagnosis in Cats

To confirm a sarcoma diagnosis, the vet will first perform a physical exam and palpate the lump to determine characteristics like location, size, and skin attachment. If sarcoma is suspected, the next step is to take a sample of the lump cells for analysis. There are two main approaches: fine needle aspiration and biopsy.

A fine needle aspirate involves inserting a small needle into the lump to extract cells, which are then examined under a microscope. This can provide a preliminary indication if cancer cells are present. However, it may not provide a definitive diagnosis.1

For a conclusive sarcoma diagnosis, a surgical biopsy is often required. This involves surgically removing all or part of the lump and sending it for histopathology testing. A vet pathologist will examine the sample under a microscope and can determine if it is cancerous based on the cell characteristics. The path report will also classify the specific sarcoma type and grade to help guide treatment. Biopsies require anesthesia but provide the most accurate results.2

Sarcoma Treatment Options

There are several treatment options that veterinary oncologists may recommend for a cat diagnosed with sarcoma:

Surgery is commonly the first line of treatment. The goal of surgery is to completely remove the tumor and surrounding tissue margins to help prevent recurrence and metastasis. Depending on the size and location of the tumor, amputation of a limb may be necessary. Wider and deeper surgical margins result in better outcomes. However, extensive surgery may not be recommended if the cancer has already spread to other areas.

Radiation therapy may be used after surgery to target any remaining cancer cells in the area and reduce the chances of recurrence. It involves a series of radiation treatments to deliver targeted high energy photons to kill cancer cells. Radiation is typically done 1-2 times per week over 3-6 weeks. Side effects can include skin irritation, hair loss, and fatigue.

Chemotherapy drugs like doxorubicin and carboplatin have shown some effectiveness against feline sarcomas. They are administered intravenously every 3 weeks for several treatments. Chemotherapy kills rapidly dividing cells like cancer cells but can also damage healthy cells. Side effects include vomiting, diarrhea, hair loss, and suppression of the immune system.

These treatments may be used alone or in combination depending on the specific details of each case. Prognosis varies widely based on multiple factors like tumor type, location, size, metastases, and feline age and health. A veterinary oncologist can advise on the best treatment options and prognosis for an individual cat.

Prognosis for Feline Sarcoma

The prognosis for cats diagnosed with sarcoma is generally guarded to poor. However, it depends significantly on the type, location, and degree of metastasis of the tumor.

For low-grade soft tissue sarcomas that are able to be completely surgically removed, the prognosis is better with median survival times of 2-3 years on average. However, higher grade or incompletely excised tumors have high rates of local recurrence, often within the first year after treatment[1].

Tumors located on the limbs have a better prognosis as full removal is often possible. Tumors occurring in the abdominal cavity or close to vital organs are more difficult to treat and carry a poorer prognosis[2].

The presence of metastasis negatively impacts prognosis significantly. Median survival times for cats with metastatic disease is often under a year. Tumor grade and location still factor into overall prognosis with metastatic sarcomas[3].

While feline sarcomas can be difficult to treat, options like surgery, radiation, and chemotherapy may extend and improve quality of life. Working closely with your vet is key to optimizing prognosis for a cat diagnosed with this disease.

Preventing Sarcoma in Cats

Unfortunately, there is no known way to completely prevent sarcomas in cats. However, there are some steps cat owners can take that may reduce the risk:

Have cats spayed or neutered. Studies show that cats who have been spayed or neutered have a lower chance of developing injection-site sarcomas as they age, compared to intact cats.[1] Spaying or neutering prevents hormone fluctuations that may promote tumor growth.

Avoid unnecessary vaccines. Work with your veterinarian to determine the core vaccines that are essential for your cat based on lifestyle factors. Consider titer testing to check antibody levels before automatically re-vaccinating. Minimizing vaccine exposure can reduce risk.

Request injections in legs/tail. Ask your vet to administer injections in areas like the legs or tail when possible, instead of around the scruff. This can make surgical removal easier if a sarcoma does develop.

Monitor injection sites. Routinely check your cat’s injection sites for any lumps, swelling, or skin changes which could signal a sarcoma. Catching it early greatly improves treatment success.

Supporting a Cat with Sarcoma

If your cat has been diagnosed with sarcoma, the most important thing is helping them stay as comfortable and happy as possible. There are several ways you can provide care and support for a cat with this condition:

Keep Them Comfortable: Make sure your cat has soft, cozy bedding and resting areas. Limit stressful interactions, loud noises, and environments that could cause anxiety. Monitor for signs of discomfort or pain and discuss options with your vet for keeping them relaxed.

Meet Nutritional Needs: Sarcoma and related treatments can make cats lose their appetite or have difficulty eating. Feed soft, appealing foods, try appetite stimulants, and ask your vet about feeding tubes if needed. Ensure adequate hydration as well. Provide nutritional supplements if recommended.

Pain Management: Work closely with your veterinarian to ensure your cat’s pain is properly managed, especially after surgery or procedures. Medications, dietary supplements, alternative therapies, and other options may help reduce discomfort.

With a little extra care and finesse at mealtimes, appropriate pain control, and keeping their environment calm, you can greatly improve your cat’s quality of life as they undergo sarcoma treatment. Focus on maximizing their comfort every day.

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