You Found a Lump On Your Cat. Now What?

Lumps on a cat’s skin are cause for concern but not alarm.


After the lymphatic system, a cat’s skin is the most common site for tumors, cysts, and other abnormal growths that manifest themselves as lumps. But it’s often the most alarming site to cat owners. Many people’s minds jump right from “lump” to “cancer.”

Pet owners find lumps so troubling that while they may avoid bringing their cat to the veterinarian’s office in general because the animal hates going, they do not hesitate when they see or feel one. “I am asked to evaluate them daily,” says Tufts veterinary internist Michael Stone, DVM.

The good news, according to Dr. Stone: Skin lumps are only rarely a manifestation of a serious disorder. Yes, sometimes a lump can signal the spread of a cancer that has originated elsewhere in a cat’s body. “But,” the doctor says, “most lumps are benign, incidental, and of little importance.”

Common types of lumps

Following are the most common types of skin growths.

Abscesses. These are lumps that contain pus. They most frequently result from a bite wound that occurs when a cat gets into a scrape with another animal. In such cases, an abscess tends to occur on a cat’s face, neck, or legs. What happens is that once a cat’s skin is punctured, blood flow to the wound area increases so the blood’s white cells can make an attempt to clean the affected area of bacteria and any other foreign material that has invaded the site. Pus forms when the white cells die and collect. The resulting lump generally bursts, but sometimes a pus-filled lump will not drain without veterinary intervention.

Whether from a bite wound or not, an abscess that does not burst also requires medical attention because it indicates a bacterial infection that did not self-resolve and can make a cat ill. Along with drainage, a prescription for antibiotics is often required.

Benign growths. The most common skin growths in cats are benign, Dr. Stone says. Benign lumps include skin lumps that grow slowly over time, typically over months to years. Lumps may also arise from insect bites, fungal infections, allergies, and adverse reactions to drugs or certain household chemicals.

Cancer. Malignant tumors are a  relatively uncommon type of growth on a cat’s skin, but they do occur. Progressive enlargement can be a clue that the lump is cancerous, but it is not a definitive clue.

Never self-diagnose

No matter what the size or appearance of a lump on your cat’s skin, you should never decide on your own what it is — or what to do about it. Any skin lump merits veterinary consultation, Dr. Stone says. You don’t want your cat to have the rare case of something serious and miss the opportunity to treat it effectively before things get out of hand.

Sometimes the doctor can make a diagnosis simply by palpating (feeling) the lump. In other cases, a needle aspiration or a biopsy (which requires sedation or anesthesia) may be required so the cells of the lump or the architecture of the tissue associated with the lump can be examined. This might especially be the case if the lump has been growing rapidly.

Depending on what’s found, the lump may simply be monitored to ensure that it doesn’t change in size or appearance. At the other extreme, surgical removal may be recommended, followed up with radiation and/or chemotherapy. But once the cause of the lump is known and dealt with, you’re not playing Russian roulette with your cat’s health.

Questions the Doctor Will Ask

When you take your cat to the vet to have a lump diagnosed, he will probably ask
the following questions:

  1. How long has the lump been present?
  2. Has it changed in size or appearance over time?
  3. Has the cat experienced any injuries in the recent past?
  4. Have there been any noticeable changes in the cat’s eating habits? (Decreased appetite in conjunction with a lump can be a clue to the seriousness of the illness.)


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