Is That Lump Cancer? How to Tell if Your Cat Has Cancer


Lumps and bumps on cats can range from benign growths like cysts to malignant tumors like cancer. According to research, 53-85% of lumps and masses found on cats end up being malignant. This makes it critically important for cat owners to carefully monitor any lumps or skin changes in their cats and have them evaluated promptly.

Cancer is one of the leading causes of death in older cats. Catching it early greatly improves the chances of successful treatment. Some warning signs that a lump may be cancerous include rapid growth, ulceration, bleeding, and discharge. The longer a malignant lump goes undetected, the more likely it is to metastasize and affect other parts of the body.

By understanding the common lump locations, warning signs, and diagnostic steps, cat owners can play a pivotal role in early cancer detection. Quick action and thorough veterinary care can help save a cat’s life.

Types of Lumps

There are several types of benign (non-cancerous) lumps that can develop on cats. Some of the most common include:


Lipomas are fatty tumors that feel soft and movable under the skin. They are usually not harmful, but can become problematic if they grow large enough to interfere with movement or other functions. Lipomas are one of the most common benign masses seen in older cats according to Non-Cancerous Masses and Tumors – Lap of Love.


Abscesses are pockets of pus caused by bacterial infections under the skin. They are usually painful, warm to the touch, and firm. Abscesses need veterinary treatment with antibiotics and drainage.


Hernias occur when part of an organ pushes through a tear or hole in the muscle or tissue holding it in place. They can cause noticeable swelling under the skin. Some hernias are present from birth while others develop after trauma or straining. Small hernias may not require treatment but larger ones will need surgical repair.


Cysts are fluid-filled sacs that can develop anywhere on the body. They are usually round, firm lumps under the skin containing liquid or semi-solid material. Sebaceous cysts are a common type of cyst filled with an oily substance produced by oil glands in the skin. Most cysts are harmless but some may require drainage or removal.


Warts are small, grainy skin growths caused by papilloma viruses. They are benign but contagious between cats. Most warts resolve on their own but some may need removal. Warts often occur around the head, neck and paws.

Warning Signs

There are several warning signs that a lump on a cat may be cancerous and require veterinary attention. Some key things to watch for include:

Rapid growth – Benign lumps tend to grow slowly, while cancerous lumps can grow quickly, sometimes doubling in size in just a few weeks. Any lump that seems to be rapidly enlarging should be checked by a vet.

Bloody or oozy – Lumps that bleed or leak fluid when touched or bumped can be a sign of cancer. This may indicate an aggressive tumor eroding through the skin. Non-healing – Sores or lumps that don’t heal within a couple weeks may be cancerous.

Changing shape or color – Benign lumps tend to be firm and consistent. Cancerous lumps often change shape, becoming irregular or misshapen. Dramatic changes in color can also indicate cancer.

According to the Pacific Santa Cruz Veterinary Clinic, “Lumps that change in appearance, sores, shabby or rough fur” could signal cancer in cats (source). Being alert to these warning signs can help facilitate early veterinary intervention.

High Risk Areas

There are certain parts of a cat’s body that are more prone to developing cancerous lumps or tumors. These high risk areas include:

Mammary Glands: Mammary tumors or breast cancer are very common in cats, accounting for 17% of all feline tumors [1]. Around 90% of mammary tumors in cats are malignant. Signs include lumps or masses in the mammary glands, ulceration, swelling, and discharge.

Lymph Nodes: Lymphosarcoma or lymphoma is one of the most common cancers seen in cats, making up 90% of all hematopoietic tumors. It involves a malignant cancer of the lymph nodes and lymphatic system. Enlarged lymph nodes may indicate lymphoma.

Mouth: Squamous cell carcinoma accounts for 60-70% of oral tumors in cats [2]. It manifests as ulcers, swellings or lumps in the mouth, tongue, gums, or throat. Difficulty eating and oral pain can occur.

Skin: Just like in humans, skin cancer is very common in cats. Look for lumps, moles or tumors that change in color or shape. The ears, nose, eyelids and mouth are high risk areas.

Diagnostic Tests

There are several diagnostic tests veterinarians use to determine if a lump on a cat is cancerous:

Fine Needle Aspirate

A fine needle aspirate involves inserting a small needle into the lump and drawing out cells for examination under a microscope. This test can often provide a preliminary diagnosis of whether cancer cells are present.1


A biopsy takes a small sample of the lump for biopsy. There are different types of biopsies. A needle core biopsy uses a larger needle to extract a cylinder of tissue. An incisional biopsy removes a portion of the suspicious lump for testing. An excisional biopsy removes the entire lump.2 A biopsy provides a definitive diagnosis.

Imaging Tests

Imaging tests like x-rays, ultrasound, CT scans, or MRI can help determine the extent of cancer spread. They allow veterinarians to see inside the body and look for masses or signs that cancer may have metastasized.1


There are several main treatment options for cancerous lumps in cats:[1]

Surgery is often the first line of treatment. The goal is to completely remove the tumor. Even if the entire tumor cannot be removed, debulking it can provide relief. Surgery can cure cancer if the entire tumor and margins of healthy tissue around it are successfully excised.

Chemotherapy uses anti-cancer drugs to kill cancer cells. It may be used before surgery to shrink tumors or after to eliminate remaining cancer cells. Chemotherapy is usually well-tolerated in cats with minimal side effects. Combining chemotherapy with radiation therapy can enhance effectiveness.[2]

Radiation uses high energy beams to kill cancer cells and shrink tumors. It may be used alone or with surgery and/or chemotherapy. Radiation therapy requires specialized equipment and expertise. Side effects are usually minimal but can include skin irritation at the treatment site.

Discussing all treatment options and their potential benefits and risks with your veterinarian is important to determine the best approach for your cat’s specific cancer diagnosis.


The prognosis for a cat diagnosed with a cancerous lump depends significantly on the type of cancer, location of the lump, and how early it was detected. According to ICatCare, early detection and treatment is key for improving outcomes. For lumps that are surgically removed in the early stages, prognosis can be quite good. However, if the cancer has already metastasized and spread to other parts of the body, prognosis worsens considerably.

For common cancers like lymphoma or mammary tumors, cats may live 9 months to a year or more with chemotherapy treatment. For very aggressive or advanced cancers, survival time without treatment is often only weeks to a couple months. Regular vet checkups and immediate attention to any new lumps or bumps can help detect cancer sooner when it is more treatable. While a cancer diagnosis is always serious, the specific type and staging makes a major difference in expected outcomes for cats.


There are some steps pet owners can take to help prevent cancer in cats:

Getting your cat spayed or neutered is one of the most important ways to reduce cancer risk. Spaying eliminates the chance of ovarian and uterine cancer, while neutering reduces the risk of testicular cancer and some prostate issues (Source).

Bringing your cat in for regular veterinary exams can help catch any lumps, bumps, or other abnormalities early on when they are most treatable. Your vet may recommend screening tests based on your cat’s risk factors and age (Source).

Limiting your cat’s exposure to sunlight can help reduce the risk of developing skin cancer. Keep cats indoors during peak sun hours, provide shade when outside, and apply pet-safe sunscreen on ears and noses (Source).

When to See the Vet

It’s important to closely monitor any new or existing lumps on your cat. You should make an appointment with your veterinarian if you notice any of the following:

  • A new lump appears, especially if it seems to grow rapidly
  • An existing lump changes in size, shape, color, or texture
  • A lump persists for more than 1 month without disappearing

According to PetMD, “any new lump that pops up on your cat should be looked at by a veterinarian.” 1 It’s better to have a vet assess any lump as soon as possible, even if it looks harmless. Catching cancer early greatly improves the chances of successful treatment.

WebMD advises bringing your cat to the vet promptly if you notice any lump that doesn’t go away within a few days after a vaccination. 2 Persistent lumps could indicate an underlying issue needing medical attention.

Don’t wait longer than 1 month before having a vet examine a lump. Early evaluation and diagnosis is key, according to Carson Veterinary Clinic. 3


To sum up the key points, lump discovery in cats can be concerning but not every lump is cancerous. Look for symptoms like rapid growth, discharge, bleeding or ulceration as red flags. Certain areas like the mammary glands, mouth and skin have higher cancer risk. Your vet can run tests like fine needle aspiration, biopsy or imaging to diagnose. Cancer treatment depends on the type and location but may involve surgery, chemotherapy or radiation. While some cats fully recover, early detection and treatment is critical.

The bottom line is do not ignore or wait on new lumps in cats. Schedule a prompt vet exam, as they can determine if it’s benign or malignant. Although cancer treatment is challenging, veterinary medicine has made great strides. With your cat’s cooperation and your dedication as an owner, there is hope. Your vet is your partner in keeping your feline healthy and providing the best care if cancer arises.

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