Mammary Tumors in Cats: Signs, Treatment, and Prognosis
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What Are Cat Mammary Gland Tumors?
Cat mammary gland tumors are formed by an abnormal mass of cells in the mammary (breast) glands. They can be benign (noncancerous) or malignant (cancerous).
Mammary gland tumors are most common in middle-aged and older female cats, but they can occur in younger female cats, as well as male cats.
Key Takeaways
- Mammary tumors in cats are often malignant and appear as lumps or swelling along the mammary chain, most commonly in middle-aged or older females.
- Early diagnosis and surgical removal are critical, as these tumors frequently spread to the lungs or lymph nodes.
- Spaying before the first heat cycle greatly reduces the risk of mammary cancer in cats.
Types of Mammary Gland Tumors in Cats
Mammary tumors are split into two categories: malignant (cancerous) and benign (non-cancerous).
Malignant (cancerous) mammary tumors are the most common type in cats and make up over 80% of mammary gland tumors diagnosed. Malignant mammary gland tumors are most often adenocarcinomas or inflammatory carcinomas. Carcinosarcomas are also occasionally diagnosed in cats. The tumors are all aggressive and will spread throughout the cat's body.
Benign tumors are uncommon in cats. This tumor type includes adenomas and fibroadenomas. Benign mammary tumors are cured with surgical resections. The only way to know if a tumor is cancerous or not definitively is to remove it and send it off for biopsy.
After a tumor is diagnosed. Surgical removal is recommended. Biopsy will help determine the type of tumor. The tumor will be graded.
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Grading refers to how aggressive the tumor is. The lower the grade the better. Mammary tumors are graded 1 to 3 with Grade 1 tumors carrying a much longer survival time than Grade 3 tumors.
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Staging refers to how advanced the cancer is. Staging looks at the size of the tumor and how much it’s spread. Mammary tumors are staged 1 to 4 with early stages carrying a much better prognosis than late stages for treatment.
Symptoms of Mammary Gland Tumors in Cats
Symptoms of mammary gland tumors in cats include:
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A lump or swelling along a cat’s mammary chain (line of breast tissue/nipples along the belly)
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Sores/ulceration on the mammary glands
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Discharge from the nipples
If the tumor has spread (metastasis), you may see other signs of illness, such as:
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Systemic (whole body) infections
Risk Factors of Mammary Gland Tumors in Cats
Risk factors of mammary gland tumors in cats include:
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Genetic predisposition: Siamese and other Oriental breeds carry a higher risk.
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Age
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Exposure to carcinogens (pesticides, cigarette smoke, etc.)
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Exposure to the sex hormone estrogen
Early spaying reduces your cat’s exposure to hormones such as estrogen and progesterone. Too many of these hormones can cause the abnormal growth of mammary tumors in cats.
When your veterinarian surgically removes your cat’s ovaries and uterus by spaying at an early age, it significantly decreases the risk that your cat will develop mammary cancer.
However, spaying is not a treatment for cat mammary gland tumors if cancerous disease has already spread throughout your cat’s body.
This makes early spaying—before your cat’s first heat cycle—so important.
How Vets Diagnose Mammary Gland Tumors in Cats
To diagnose mammary gland tumors in cats, vets will begin with a complete physical exam.
Vets will be suspicious of this tumor based on appearance alone, but accurate diagnosis of cat mammary gland tumors requires microscopic examination of tissue.
Other tests a vet will recommend include:
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Cytology (test for abnormal cells)
This biopsy report typically tells the veterinarian the following information:
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The type of the tumor
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The origin of the tumor
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The grade of the tumor
The stage of the tumor is also determined by further diagnostic testing, such as:
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Abdominal ultrasound
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Lymph node needle sampling
These tests investigate if the tumor has spread to other parts of the body.
Treatment for Cat Mammary Gland Tumors
Treatment of cat mammary gland tumors typically include surgical removal of the affected tissue. This prevents the cancer from spreading to other parts of the body.
The veterinary surgeon may even recommend removing the whole mammary chain, along with the accompanying lymph nodes.
Prognosis of Mammary Tumors in Cats
After surgery cat mammary gland tumor surgery, chemotherapy and/or radiation therapy may be recommended.
Recurrence or metastasis (spread) is likely, and survival times are usually not longer than a year.
Recovery and Management of Mammary Tumors in Cats
Recovering from mammary tumor surgery will take roughly 10 to 14 days.
During that time, it is important that you keep your cat’s activity to a minimum.
Avoid letting them jump up on high surfaces and consider keeping them in a crate with a litter box, food and water.
Alternatively, a small room without high surfaces can help minimize activity.
A recovery cone or recovery suit is also recommended to prevent licking/chewing at the incision while the surgery site is healing.
If your cat is in pain or stressed during recovery, they may benefit from gabapentin. Gabapentin helps with both anxiety and pain in cats.
How To Prevent Mammary Tumors in Cats
Spaying before a feline’s first heat cycle is the single best way to prevent mammary cancer in cats.
Eliminating your cat’s exposure to other known carcinogens—such as cigarette smoke and BPAs—may also be helpful.
Mammary Tumor in Cats FAQs
What does mammary cancer look like in cats?
Mammary cancer looks like lumps or bumps on their belly near or around their nipples.
How can your veterinarian tell if a mammary mass is benign or cancerous?
The only way to tell for sure if a mammary mass is benign or cancerous is to surgically remove the mass and send it off for biopsy.
