Surface tumors are common in cats. It is often impossible to determine whether a surface tumor is benign or malignant by appearance alone. The only conclusive way to make a diagnosis is by biopsy, a procedure in which tissue or cells are removed by your veterinarian and examined under a microscope by a veterinary pathologist.
For small tumors, it is best for your veterinarian to remove the growth and present the entire specimen to the pathologist. For tumors larger than 1 inch (25 mm) across, it may be advisable for your veterinarian to obtain a tissue sample by fine needle aspiration. In this procedure, a needle connected to a syringe is inserted into the tumor and cells are obtained by pulling back on the plunger. Alternatively, the vet can use a cutting needle to obtain a core sample. An open biopsy, in which an incision is made, is preferred for suspected sarcomas and tumors that present diagnostic problems for the pathologist.
Although the name suggests otherwise, ringworm isn’t caused by a worm at all-but a fungus that can infect the skin, hair and nails. Not uncommon in cats, this highly contagious disease can lead to patchy, circular areas of hair loss with central red rings. Also known as dermatophytosis, ringworm often spreads to other pets in the household-and to humans, too.
Epidermal inclusion cysts, also called sebaceous cysts, are benign tumors that arise from glands found beneath the skin. They can occur anywhere on the body. Although less common in cats than in dogs, they are still the most common surface tumor in cats.
A sebaceous cyst is made of a thick capsule that surrounds a lump of cheesy material called sebum. It may grow to 1 inch (25 mm) or more. Eventually, it is likely to become infected and will have to be drained. This sometimes leads to a cure.
Treatment: Most cysts should be removed. Cysts can often be removed by electrocautery or cryotherapy. At the very least, sedation and a local anesthetic will be required, and many cats may need general anesthesia.
Warts and Papillomas
These growths are not nearly as common in cats as they are in people. They tend to occur on the skin of older cats. Some are on a stalk, while others look like a piece of chewing gum stuck to the skin.
Treatment: If they become irritated or start to bleed, they should be removed. In general, they are not a threat to the health of the cat.