Lumps and Bumps. What Those Hard Lumps in Cats Really Mean


Lumps and bumps are common findings in cats. According to the Animal Cancer Foundation, 6 million new cancer diagnoses are given to cats every year. Cancer is one of the leading causes of death in cats, with over 1.9 million cats dying from cancer annually in the United States alone.

The purpose of this article is to discuss the various types of lumps that can develop in cats, their potential causes, warning signs to look out for, how lumps are diagnosed, treatment options for benign and cancerous lumps, ways to help prevent lumps, and when you should take your cat to see the vet. We will provide an overview of the key things cat owners should know related to lumps and bumps on their feline companions.

Common Lump Locations

Some of the most common places for lumps to develop on cats include:

  • Head and neck – Areas like the chin, cheeks, and throat often develop lumps like mast cell tumors. The head is susceptible due to exposure and activity in grooming, feeding, etc. [1]
  • Legs and paws – Lipomas or fatty tumors tend to occur on the legs and paws, especially in overweight or older cats. This may be due to decreased activity. [2]
  • Torso – Lumps may appear anywhere on the body but are common along the flank, back, and sides. Areas that receive less grooming and have loose skin/fat are prone to lumps.
  • Mammary glands – Female cats are at risk for mammary tumors and cancer along the milk line and teats.

In general, areas of the body that receive less grooming, sunlight, or activity seem more susceptible to abnormal lumps and growths. The head, legs, and underside are common sites.

Types of Lumps

There are several different types of lumps that can develop on a cat’s body. Some of the most common include:

Lipomas: Lipomas are benign fatty tumors that feel soft and movable under the skin. They are very common in older cats and usually harmless, though they can grow large. According to WebMD, lipomas account for up to 50% of all skin masses found in cats.

Abscesses: Abscesses form when bacteria gets trapped under the skin, often from a bite wound. They are pocketed infections filled with pus and feel like soft, fluid-filled lumps. Abscesses need to be treated with antibiotics and by draining the infection.

Cysts: Cysts are fluid-filled sacs that form within tissue or under the skin. Sebaceous cysts are common in cats and contain sebum and dead skin cells. They often rupture on their own and heal without treatment. According to PetMD, cysts feel like small movable lumps under the skin.

Hematomas: Hematomas occur when blood vessels rupture and cause localized bleeding outside the blood vessels. This forms a fluid-filled swelling. Hematomas can develop from trauma and often resolve on their own as the blood is reabsorbed.

Malignant tumors: Cancerous tumors like squamous cell carcinoma and mast cell tumors can arise on the skin or subcutaneously. They may feel firm, fixed, and appear ulcerated. As PetMD notes, tumors require surgical removal and may necessitate chemotherapy or radiation.

It’s important to have any new, growing, or suspicious lumps examined by a vet to determine if they are benign or malignant. Your vet can perform tests like a fine needle aspirate to diagnose the type of lump.

Causes of Lumps

There are various causes of both benign and malignant lumps in cats. Some of the most common causes include:

Trauma – Injuries or trauma to the skin, such as bites or scratches, can cause abscesses or hematomas which appear as lumps. These are usually benign.

Infections – Bacterial, fungal or viral infections can lead to localized inflammation and lumps under the skin. For example, abscesses, cysts or reactions to flea bites. These are typically benign.

Cancer – Feline lymphoma, mast cell tumors and fibrosarcomas are some of the more common cancers that can cause lump formation. Cancers often start as small, firm nodules that progressively enlarge. Cancerous lumps tend to be fixed/immobile and fast growing.

Hormonal – Hormonal imbalances can stimulate overgrowth of glandular or fatty tissue. For example, thyroid conditions may cause symmetric thyroid nodules. Obesity can cause benign fatty tumors called lipomas.

Allergies/Reactions – Allergic reactions to drugs, vaccines or insect bites can prompt localized swelling and lumps. These types of lumps are usually transient.

According to one source, “Causes of lumps in cats can be broken down into inflammatory, infection, tumors, and cysts” (Petplan). It’s important to have any new or changing lumps evaluated by a vet to determine the underlying cause.

Warning Signs

There are several warning signs that may indicate a lump on a cat is cancerous rather than benign:

Rapid growth – Benign lumps tend to grow slowly, while cancerous lumps can grow quickly in a matter of weeks or days.

Ulceration – Cancerous lumps may ulcerate, opening up and becoming an ulcer on the skin.

Irregular edges – Cancerous lumps often have irregular or poorly defined edges, while benign lumps tend to have smooth, well-defined edges.

Firmness – Cancerous lumps are usually firm or hard compared to benign lumps.

Fixed – Cancerous lumps are often fixed in place and immovable, while benign lumps may move freely under the skin.

Necrosis – Cancerous lumps may exhibit necrosis in the overlying tissue, which is tissue death.

Bleeding or discharge – Cancerous lumps may bleed or leak fluid easily if ulcerated.

Non-healing – Benign lumps will often shrink or disappear, while cancerous lumps persist and continue to grow.

Metastasis – Cancerous lumps can spread to other parts of the body.

Discomfort – Cancerous lumps may cause pain or discomfort for the cat.

Location – Certain locations like the mammary glands, mouth, and skin increase cancer risk.

If a lump on your cat exhibits any of these warning signs, it is important to have your veterinarian evaluate it as soon as possible to determine if it is cancerous.

Diagnosing Lumps

Veterinarians use several diagnostic tests to determine the cause of lumps in cats. The tests help differentiate between benign masses like cysts or warts, and more serious cancers like lymphoma or mast cell tumors. The main diagnostic methods include:

  • Physical exam – The vet will thoroughly inspect and palpate the lump, noting its size, texture, mobility, and whether it seems to bother the cat. This provides initial clues about the lump’s nature.
  • Fine needle aspirate – A needle and syringe are used to extract cells from inside the lump for examination under a microscope. This is a simple in-office procedure that can help identify some types of growths.
  • Biopsy – Taking a small sample of the lump for microscopic analysis gives the most definitive diagnosis. Biopsies are done either by surgical excision or with a needle core device.
  • Imaging – X-rays, ultrasound, CT or MRI scans create internal images that show the lump’s size, shape and connections to surrounding tissue. Imaging aids surgical planning if the mass must be removed.

While fine needle aspirates and biopsies provide the most diagnostic information, imaging is also important to see the extent of the lump’s growth. Using multiple tests provides veterinarians with the clearest possible picture of the type of lump present and determines the best treatment approach. For more information see this PetMD article.

Treating Benign Lumps

For many benign lumps like lipomas or cysts, the vet may recommend just observing the lump initially and only taking action if it grows or causes discomfort. According to Merck Veterinary Manual, benign lumps that don’t impact the cat’s quality of life often don’t require treatment.

If the lump grows large enough to interfere with movement or becomes irritated, treatment may involve draining fluid from cysts or surgically removing benign masses. According to VRA Veterinary Hospital, lipomas that cause discomfort can be surgically removed. The vet will numb the area, make an incision to remove the entire lump, then close the incision with sutures.

For recurring sebaceous cysts, the vet may recommend surgically removing the cysts along with the surrounding glandular tissue to prevent further cysts from developing, according to PetMD. While benign lumps can often be left alone, surgical removal is an option if they negatively impact the cat’s health or quality of life.

Treating Cancerous Lumps

If a lump is diagnosed as cancerous, there are several treatment options available, though the specific treatment will depend on the type and stage of cancer. Some of the most common cancer treatment options for cats include:

Surgery – This involves surgically removing the tumor. Surgery is often the first line of treatment and the most likely to result in a cure if the cancerous lump can be fully removed. However, cancer can recur in other areas if some cancer cells remain after surgery. According to ICATCare, surgery results in a cure for approximately 90% of cats with skin cancer and 50% of cats with breast cancer.[1]

Chemotherapy – Cytotoxic drugs are used to kill cancer cells. According to PetMD, cats tend to tolerate chemotherapy well with minimal side effects. It is often used after surgery when cancer cells may remain. Certain cancers like lymphoma usually require chemotherapy as the main treatment.[2]

Radiation Therapy – High energy radiation is used to kill cancer cells and shrink tumors. Radiation may be used alone or with other treatments like surgery or chemotherapy. It is commonly used to treat nasal tumors, brain tumors, and cancers that cannot be completely removed with surgery.

Immunotherapy – Drugs that stimulate the immune system to attack cancer cells may be used alone or with other treatments. Immunotherapy is a newer cancer treatment option for cats that holds promise for some forms of the disease.

Nutraceuticals – Natural supplements with anti-cancer effects may help combat cancer according to some holistic veterinarians. However, more research is needed to confirm their efficacy.

The prognosis and success rate for treating cancerous lumps varies considerably based on the specific type and stage of cancer. Working closely with your veterinarian is essential to determine the best treatment plan for your cat.


Preventing Lumps

There are a few ways cat owners can help prevent lumps from developing on their cats:

Flea control – Fleas can cause irritation, scratching, and infections that lead to abscesses. Using regular flea prevention medication can reduce this risk. Products such as monthly topical treatments and flea collars can kill fleas and their eggs before they cause problems.

Avoid trauma and injuries – Lumps can form at sites of trauma like bites or scratches. Keeping cats indoors, trimming their nails, and separating fighting pets reduces these risks. Handling cats properly can prevent accidental injury.

Spay/neuter your cat – Intact female cats are at higher risk for mammary cancer. Spaying before 6 months old greatly reduces this risk. Neutering male cats also has some cancer prevention benefits.

Vaccinate against viruses – Feline leukemia virus and some other viruses are linked to increased cancer rates in cats. Following your vet’s recommended vaccine schedule can provide protection.

Routine vet exams – Checking for lumps during annual exams allows early treatment if any are found. Monitoring lumps over time is important, as rapid changes can signify cancer.

While not all lumps can be prevented, these steps can reduce known risk factors. Talk to your vet about lump prevention specific to your cat’s health and lifestyle.

When to See the Vet

If you notice any lumps or bumps on your cat, it’s important to have them examined by a veterinarian, even if they seem harmless. According to Mobile Vet MD, some signs that warrant an urgent vet visit include:

  • Rapid growth of a lump over 2-4 weeks
  • Ulceration, bleeding, or discharge from a lump
  • Difficulty eating or swallowing
  • Weight loss
  • Lethargy or lack of appetite
  • Difficulty breathing

Lumps that are rapidly growing, bleeding, or causing other symptoms are more likely to be cancerous. According to PetMD, your vet will assess the lump by looking at its size, texture, mobility, and location on your cat’s body.

The bottom line is – if you notice any concerning lumps or bumps on your cat, don’t wait to make a vet appointment. Catching cancerous lumps early greatly improves the chances of successful treatment. Trust your instincts if you feel something is off with your furry friend.

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