If you find a lump on your dog or cat, don't panic. Here's what to expect when getting it checked out.

Weekly Newsletter The best of The Saturday Evening Post in your inbox! Join

If you have an aging pet, you may periodically find some kind of lump or bump on its skin, or maybe even deeper. If you’re like me, your mind probably jumps first to the thought–is it cancer?

According to Dr. Laura Garrett, veterinary oncologist at the University of Illinois Veterinary Teaching Hospital in Urbana, dogs and cats get cancer at the same rate that people do. But, she says, finding a lump or bump doesn’t automatically mean something malignant or fatal.

A lump that you may find on your pet could be one of several things: an infection, such as an abscess from a dog or cat bite; inflammation, like a small, localized reaction to a vaccine or a bug bite; or a tumor, meaning an abnormal growth of cells, which could be either benign (harmless) or malignant (invasive and potentially harmful to your pet’s health). The best way to determine the origin of the lump, and the best thing for your pet’s health, would be to have it examined by your veterinarian.

Subscribe and get unlimited access to our online magazine archive. Subscribe Today

Typically, a veterinarian will measure the lump and then take a fine-needle aspirate. This is a process in which a small needle is used to take a sample of the cells in the lump. The veterinarian will then view the cells under a microscope to get an initial idea of what is causing this mass (another word for “tumor”). In most cases, the sample is then sent off to a lab of experts for a final evaluation.

“No doctor can determine if a mass is ‘safe’ just by looking at the lump itself or by feeling it,” Dr. Garrett says. That means that neither you nor your veterinarian can be certain that a mass is harmless without getting a microscopic look at the cells within via a fine needle aspirate or a biopsy.

If you do find a mass on your pet, you should be prepared to answer a few questions for your veterinarian: Have any changes occurred since you first noticed the mass? Does the mass seem to bother your pet? Has it been oozing any fluid or blood? If you answer “yes” to any of these questions, it might be a cause of increased concern, but answering “no” does not eliminate the possibility that the lump is a health risk.

Fortunately for middle-aged to older dogs, the most common lump they get is a lipoma–a benign, fatty growth. Most lipomas never become a problem, and also have nothing to do with the weight of the animal. Dr. Garrett recommends, “Lipomas usually need to be removed only if they are in a spot that bothers the pet or the owner or if the lump begins to change quickly.”

If the lump is not a lipoma, your veterinarian will try to determine what type of tumor is. If this can’t be done at your clinic, a cell sample or larger biopsy may need to be sent to a specialty diagnostic lab for examination.

If a tumor is malignant, your veterinarian will determine whether it has spread to other parts of the body by taking a fine-needle aspirate of lymph nodes, taking chest X-rays, or sometimes doing an ultrasound of the animal’s abdomen. A specialty oncologist such as Dr. Garrett has the knowledge of what tumors commonly spread, where they spread to, and how to treat them. Your veterinarian may refer you to a specialist if testing or treatment can’t be done at your regular clinic.

Treatment for malignant tumors depends on what type of cancer it is, but the range of options is very similar to what is available for human cancer patients. If the location of the tumor permits, surgery may be performed to remove it. Other tumors may be treated with various forms of chemotherapy. Luckily, dogs and cats usually tolerate chemotherapy much better than people.

“About 20 percent of pets have mild gastrointestinal upset, such as vomiting, diarrhea, or decreased appetite. A similar percent of pets may have low white blood cell counts that can predispose to infections, but a count so low that it can be life-threatening happens less than 3 percent of the time. Hair loss may be seen in dogs whose hair coats grow continuously (like poodles), but most dog breeds do not experience hair loss. Cats may lose their whiskers and guard hairs, making their coats more of a fluffy texture,” Dr. Garrett says.

Many cancers in cats and dogs can be cured if caught early and treated appropriately, according to Dr. Garrett. Getting new lumps and bumps examined by your veterinarian may prevent a disease from becoming more severe. Be sure to check with your local veterinarian if you have questions or concerns about your pet’s lumps and bumps.

Julia Disney is an Information Specialist at University of Illinois’ College of Veterinary Medicine.