According to Dr. Selmic, surgery alone cures the majority of mast cell tumor cases.
Dr. Laura Selmic, a veterinarian who joined the faculty at the University of Illinois Veterinary Teaching Hospital in Urbana in September, is among the 36 veterinary surgeons who were the first to be designated as Fellows of Surgical Oncology by the American College of Veterinary Surgeons in 2012.
“Surgery is the most common technique for treating cancer in companion animals,” says Dr. Selmic. “The goal of surgery is to control or eliminate the local cancer to improve the patient’s quality of life.”
Cancers of the skin, mouth, gastrointestinal tract, liver, pancreas, adrenal glands, kidneys, and bladder are all treated primarily with surgery. Among cancers of the skin, mast cell tumors and soft tissue sarcomas are very common candidates for surgery.
Mast cell tumors account for nearly one-fifth of all skin tumors in dogs. Mast cell tumors can occur in any breed of dog, but breeds with an increased risk for this type of tumor include Labrador and golden retrievers, cocker spaniels, schnauzers, Staffordshire terriers, beagles, Rhodesian ridgebacks, Weimaraners, Shar Peis, and dogs of bulldog descent, such as boxers, Boston terriers, English bulldogs, pugs.
Dr. Selmic explains that most mast cell tumors are found as a bump on the skin. To determine whether the lump is cancerous, a veterinarian will perform a fine-needle aspirate, a procedure in which a small needle is placed into the mass to collect cells. The cells are then examined under a microscope.
“Mast cell tumors mostly grow locally but occasionally can metastasize (spread) to lymph nodes or other areas of the body,” says Dr. Selmic.
For this reason, sometimes after a mast cell tumor is diagnosed, other tests may be recommended to check for metastasis. These tests may include fine-needle aspirate of a lymph node and an ultrasound of the abdomen. Occasionally chest X-rays are used to look for lymph node enlargement in the chest. Pre-surgical blood work and sometimes a urine test are needed to check general health prior to anesthesia.
If the tumor is small or restricted to the local area, the dog is a good candidate for surgery. If there is spread to a lymph node, surgery may include removal of that lymph node and chemotherapy may be recommended after the surgery. Rarely, if there is spread to multiple areas of the body at diagnosis, chemotherapy may be the best option.
“The surgeons will remove the tumor and two to three centimeters of normal tissue surrounding it, as well as the outside covering of the underlying muscle, to try to ensure that the tumor is completely removed,” explains Dr. Selmic.
The excised tumor is submitted for biopsy for a pathologist to examine and determine if the cancer cells have been removed completely. Often the patient can go home the day of surgery, although at times an overnight stay is needed.
To promote uncomplicated healing after removal of a skin tumor, the dog must be confined and allowed outside for short leash walks only for toilet purposes. An Elizabethan collar is useful to prevent the dog from scratching or licking the incision, which could lead to an infection of the site. Close observation of the dog may be needed to prevent trauma to the area.
A re-check is usually scheduled 7 to 14 days after surgery to assess the surgical site. At this time, if skin sutures or staples were placed, these are often removed. At this appointment recommendations will be made for follow-up depending on the biopsy results.
According to Dr. Selmic, surgery alone cures the majority of mast cell tumor cases. The biopsy results tell the surgeon if the tumor was completely removed and whether the tumor appears to be of an aggressive type.
If the mast cell tumor invades deeply or has spread over a larger area than expected, chemotherapy may be recommended. If the tumor is located in an area, such as the lower leg, that makes the tumor difficult to remove with wide margins and cells may remain after surgery, a repeat surgery or radiation therapy can be used to reduce the chance of recurrence.
“Unfortunately there is no way to prevent dogs from developing a mast cell tumor. However, close attention to lumps and bumps on your dogs can help early detection of cancers,” says Dr. Selmic.
For more information about cancer in pets, speak with your veterinarian or seek a surgical oncologist.
By Sarah Netherton