Soft or Solid? The Mysterious Texture of Feline Tumors


Feline tumors and cancer are relatively common in cats. Studies show that approximately 1-2% of cats will develop tumors over their lifetime (MacVean, 1978; Pérez-Enriquez, 2020). The most common types of feline tumors include carcinomas, sarcomas, adenocarcinomas, lymphomas, and adenomas (Pérez-Enriquez, 2020). Mammary tumors are also very prevalent in cats, with almost 90% being malignant (CSU Animal Cancer Center). Feline tumors can be benign or malignant, and early detection and treatment is key for the best prognosis.

Benign vs Malignant Tumors

Benign tumors are noncancerous growths that do not invade nearby tissue or spread to other parts of the body (source). They grow slowly, have distinct borders, and can often be surgically removed. Malignant tumors are cancerous growths that can invade and damage nearby tissue and spread to other sites in the body (source).

The main differences between benign and malignant feline tumors are:

  • Benign tumors have distinct borders and do not spread. Malignant tumors often have irregular borders and can spread to other parts of the body.
  • Benign tumors typically grow slowly. Malignant tumors tend to grow more rapidly.
  • Benign tumors usually do not recur after surgical removal. Malignant tumors may recur locally or spread distantly after removal.
  • Cells from benign tumors resemble normal cells and are usually well differentiated. Cells from malignant tumors do not look normal and are poorly differentiated.
  • Benign tumors do not invade or damage nearby tissues. Malignant tumors can invade nearby tissue.
  • Benign tumors are rarely life threatening. Malignant tumors can be life threatening if untreated.

Common Benign Tumors

Some of the most common benign (non-cancerous) tumors found in cats include:

Lipomas – These are benign fatty masses that develop under the skin. According to the Merck Veterinary Manual, lipomas are the most common skin tumor diagnosed in cats [1]. They feel soft and movable under the skin. Lipomas usually form on the torso, limbs, and head. While generally non-problematic, lipomas can occasionally impair movement if they grow large enough. Surgical removal may be required in some cases.

Sebaceous adenomas – These benign tumors arise from sebaceous glands in the skin. Sebaceous adenomas often appear as solitary, hairless nodules on the head, neck, and torso. They are usually slow growing and painless. Surgical removal is curative if needed for cosmetic reasons or if the mass becomes problematic [2].

Papillomas – Feline viral papillomas are benign skin tumors caused by a contagious virus. They typically form wart-like growths on the face, neck, legs, and body. Papillomas often regress on their own within a few months. But surgical removal may be required for persistent or problematic lesions [1].

Common Malignant Tumors

Some of the most common malignant (cancerous) tumors in cats include:


Lymphoma is a cancer that originates in the lymph nodes and lymphatic system. It is one of the most common feline cancers, accounting for up to one third of all cat cancers [1]. Lymphoma most often affects middle-aged to older cats, and occurs more frequently in cats positive for feline leukemia virus (FeLV) or feline immunodeficiency virus (FIV) [2].

Squamous Cell Carcinoma

Squamous cell carcinoma is a cancer that originates from squamous epithelial cells, such as those in the mouth, skin, bladder, and digestive tract. It is one of the most common oral cancers in cats, usually occurring on the tongue, gums, or tonsils. It can be locally invasive and may metastasize to local lymph nodes [1].


Fibrosarcomas are tumors that originate from fibrous connective tissue cells. In cats, they most commonly occur at injection sites, believed to be caused by local inflammation from vaccinations. Fibrosarcomas are locally invasive into surrounding tissue and tend to recur after surgical removal [2].

What Causes Feline Tumors?

The exact causes of tumors in cats are complex, but research has identified several factors that may contribute to their development:

Genetics play a role. Some breeds, like Siamese cats, may have a genetic predisposition to developing certain types of cancer.

Environmental factors are also implicated. Exposure to things like second-hand smoke, pesticides, and sunlight can increase a cat’s risk.

Certain viruses are associated with tumor formation in cats. Feline leukemia virus and feline immunodeficiency virus damage the immune system, allowing cancer cells to grow. The feline sarcoma virus can directly trigger tumor development.

Diagnosing Cat Tumors

A veterinarian will start the diagnostic process for tumors in cats by performing a thorough physical exam to check for any abnormalities or signs of illness. The vet will pay close attention to any lumps, bumps, or masses on or under the skin and note their location, texture, mobility, and whether they seem to be painful (Viera Vet).

If a suspicious mass is found, the next step is to take a sample of cells or tissue through a biopsy procedure. There are different types of biopsies including fine needle aspiration, core needle biopsy, incisional biopsy, and excisional biopsy. The biopsy sample is then sent to a lab for analysis to determine if cancerous cells are present and identify the tumor type (Drake Center).

Some other diagnostic imaging tests vets may use include x-rays, ultrasound, CT scan, or MRI. These images allow the vet to see the size, shape, and location of any tumors in the body. They can also help detect if the cancer has metastasized and spread to other areas (PetCure).

Hard vs Soft Tumors

Feline tumors can present in different ways, with some being firm or hard masses while others are soft or fluid-filled lumps. The hardness or softness of a tumor can provide clues about whether it is benign or malignant.

Hard tumors often indicate a solid mass growth. Two of the most common hard tumors in cats are:

Soft or fluid-filled lumps may indicate a cyst or benign fatty tumor. Some common soft tumors include:

  • Lipomas – benign fatty tumors that feel soft and movable under the skin
  • Sebaceous cysts – fluid-filled lumps under the skin often on the head or back

However, it’s important to note that some malignant tumors can also present as soft lumps in cats. So any new lumps or bumps should be checked by a veterinarian, regardless of whether they are hard or soft.

Treating Feline Tumors

Treating feline tumors often involves a combination of surgery, chemotherapy, and radiation therapy. Surgery is typically the first line of treatment and the most effective for cats. The goal of surgery is to completely remove the tumor. For small tumors that have not spread, surgery may be curative. For larger or more invasive tumors, surgery can debulk the tumor and prolong survival.

Chemotherapy may be recommended after surgery to target any remaining cancer cells. Chemotherapy drugs most commonly used for cats include carboplatin, doxorubicin, and lomustine. Cats tend to tolerate chemotherapy better than humans with less severe side effects. However, possible side effects can include gastrointestinal issues like vomiting or diarrhea.

Radiation therapy uses high-energy radiation to kill cancer cells and shrink tumors. It may be used alone or with surgery and/or chemotherapy. Radiation can be very effective for treating certain types of feline cancers. Side effects are usually minimal but can include skin irritation and fatigue.

According to, the combination of surgery, chemotherapy, and radiation offers the best chance of long-term control or cure for many types of malignant feline tumors.


The prognosis for feline tumors depends on several factors including the type of tumor, the size of the tumor, and whether it has metastasized or spread to other parts of the body. Some types of feline tumors can have a good prognosis if caught and treated early. For example, many benign tumors like lipomas are encapsulated and do not tend to spread, so surgical removal results in a cure. However, other types of feline tumors have a poorer prognosis overall.

Malignant tumors like lymphosarcomas tend to be more aggressive and have higher chances of spreading to other organs, which negatively impacts prognosis. In one study, cats with lymphosarcoma that received chemotherapy had a median survival time of just under 1 year after diagnosis[1]. Larger tumor size is also associated with poorer prognosis, as larger masses have had more time to potentially spread. Cats with late stage metastatic cancer that has already spread have a grave prognosis in most cases.

In summary, feline tumor prognosis varies significantly based on tumor type, size, metastasis, and other factors. Working closely with a veterinarian for early detection, accurate diagnosis, and prompt treatment initiation offers cats the best prognosis when facing these conditions.


There are steps cat owners can take to help prevent tumors and cancer in cats:

Spaying or neutering cats helps prevent certain types of reproductive cancers. Spaying female cats eliminates the risk of uterine and ovarian cancer, while neutering male cats prevents testicular cancer and reduces the risk of prostate cancer.

Avoiding secondhand smoke exposure is also important. Cigarette smoke contains carcinogens and toxins that can increase a cat’s cancer risk. Keep cats away from smokers and do not allow smoking inside your home.

Feeding your cat a high-quality diet with antioxidants can also be beneficial. Poor nutrition and obesity raise cancer risk. Choose a balanced cat food made with real meat, fruits and vegetables. Avoid cheap brands with fillers. Keep your cat at a healthy weight through diet and exercise.

While not definitive, some research indicates supplements like turmeric may have anti-cancer effects. Consult your vet before giving supplements.

Regular vet checkups to screen for cancer are also advised, especially as cats age. Catching cancer early greatly improves treatment success.

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