I found a lump on my dog that is about the size of a large marble. It is located under the skin, just above the knee, and does not seem to give him discomfort or pain.  Is there a cause for concern?

Always get a vet to check out a lump.

A lump may indicate cancer, but many such growths can be harmless. You mentioned that it is not painful or bothersome, but several different types of dangerous growths can have those characteristics.

Any time a lump is seen or felt on an animal, it deserves to be tested to determine whether it is cancerous or just a benign, non-cancerous lump. It is critical that you take your pet to your veterinarian for examination. He or she may wish to perform a fine-needle aspirate on the mass, or other appropriate tests. A fine-needle aspirate is performed quickly, without the need for sedation in most patients.

A fine-needle aspirate involves taking a small needle and placing it into the mass. A syringe is used to aspirate the cells of the growth into the needle. These cells are then put onto a slide, stained, and evaluated under a microscope by the veterinarian or by a veterinary pathologist. The study of these stained cells is called cytology. This tiny sample of cells often provides important information about the growth's nature. The test can separate benign fatty growths called lipomas from other serious problems that may require treatment.

When the fine-needle aspirate does not provide a diagnosis, the veterinarian often recommends a biopsy. A biopsy involves taking a large piece of tissue from the growth, or surgically removing the growth. This usually requires sedation or anesthesia. The tissue must be processed and analyzed by a pathologist, which takes several days.

Any mass or growth on a dog, cat, or other animal needs to be assessed. A fine-needle aspirate is simple to do, inexpensive, and may provide a rapid diagnosis.

05/04/06