Diagnosing Cancer

Cancers can cause a wide variety of signs in your dog and mimic other disease processes. They are often accompanied by other health problems and may have very nonspecific symptoms. There are many changes you may notice in your dog that push you to schedule a veterinary visit. Once you arrive at your veterinarian's, there are a wide variety of tests that can help diagnose cancer and guide the treatment plan for specific cancer. Remember, “cancer” is really a catchall word that doesn't describe a specific disease.

Signs You Might See

The problems your dog might experience depend greatly on the type and location of her cancer. In general, dogs with any type of cancer will show some weight loss. This may be related to a decrease in appetite or perhaps to the draining of nutrients by the cancer as it grows. Many dogs show a decrease in activity and stamina. Instead of a mile walk, your dog may want to turn back early.

Depending on the specific cancer, your dog could have vomiting or diarrhea. She could be lame or act pained when touched in certain areas. Dogs with cancers of nerve tissue may have an uncoordinated gait. You may notice an actual lump on your dog, such as a large fatty tumor or lipoma on the rib-cage area. It could be a small lump — mast cell tumors as tiny as a small bug might be noticed on a shorthaired dog. A dog may have a sore that fails to heal or a discolored area on the skin. Dogs with growths in their mouths often drool or pant more than usual.

Diagnostic Testing

Testing for cancer usually starts with a complete blood panel. Your veterinarian will check that all the main body systems are fine. All areas of the body will be examined for cancer and to determine whether your dog is healthy enough to handle treatment if a cancer is found. Any obvious lumps or bumps may have a needle aspirate taken, be surgically biopsied, or even be totally removed.

Your veterinarian may try to examine some cells right in the office, but often tissue samples need to be sent out to a veterinary pathologist. Veterinary pathologists are specialists in examining tissues for any abnormalities. They will process the sample, maybe using special stains, and examine the cells under a microscope.

An FNA is a fine needle aspirate. Your veterinarian will put a needle into a suspicious growth and draw out some cells. These cells are then checked under a microscope for any indications of cancer. You can get “false negatives” — when you feel there is no cancer, but in truth, the needle sample simply missed the area of cancer cells and only sampled normal cells. Still, a positive result gives you a quick diagnosis.

Along with these laboratory tests, many dogs will need X rays or ultrasound examinations. It is traditional to check chest X rays for any sign of cancer spread. Three views are best; left side, right side, and with the dog on his back. Ultrasound can also be used to carefully locate any unusual growths or even to guide a biopsy attempt.

Sometimes, despite all this information, the best way to get a definitive diagnosis is to do an exploratory surgery. Your veterinarian can then take biopsy samples, possibly remove any growths, and check to see that other tissues and organs all appear healthy.

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