Tumor of the Uterus in Dogs

The chance of your dog getting uterine tumors is relatively small. Uterine tumors (both leiomyomas and leiomyosarcomas) are preventable by having your dog spayed before she goes into estrus (heat) for the first time. This can happen any time after your dog is three months old, so it is important to get her fixed before she is six months old. Removal of the female reproductive organs not only prevents uterine tumors, but also lowers the incidence of mammary tumors and eliminates the risk of uterine infections. Every year that your dog has not been spayed increases her chances of getting uterine cancer tremendously, so it is important that you do so if you do not plan to breed your dog.

There are two types of uterine tumors in dogs, which are leiomyomas (noncancerous) and leiomyosarcomas (cancerous). Although uterine tumors are rare in dogs, leiomyomas are the most common of the two, and are found in the smooth muscle of the walls of any organ, such as the uterus. These types of tumors are separated from other parts of the body, not very large, and do not usually spread. Leiomyosarcomas only account for about 10% of all uterine tumors, which is fortunate because they are cancerous and may spread to other parts of the body unless surgically removed. They can both cause similar symptoms, or no symptoms at all until the tumor gets large enough to affect bodily functions. Like most types of cancer, these are most often reported in older dogs, but can affect females of all breeds at any age if they are not spayed.

Most often, neither canine leiomyosarcomas or leiomyomas show any symptoms until they are large enough to cause damage to other vital organs. When symptoms of either one of these tumors are reported, the most common is discharge from the vaginal area. Some other symptoms that may be observed are:

• Abdominal pain and swelling
• Loss of appetite
• Visible weight loss
• Vomiting
• Constipation
• Excessive sleepiness
• Weakness
• Depression
• Increased thirst and frequent urination
• Incontinence
• Blood in urine
• Lack of interest in exercise or playing

 Types

• Canine leiomyomas are usually benign (non-cancerous), and affect older female dogs that have not been spayed
• Canine leiomyosarcomas are malignant (cancerous), and affect females of any age that have not been spayed

• Endometrial hyperplasia (overgrowth) of the uterus is usually due to stimulation by the natural female hormone progesterone, which remains elevated for up to two months after estrus in the dog
• External sources of estrogen and progesterone (sometimes given medically for control of estrus cycles) can also induce the same pathology
• Previous uterine infections

When you visit your veterinarian, you will be asked when the symptoms started, how your dog’s general health has been, and whether she has been acting differently lately. Be sure to provide him with your dog’s vaccination record if you have not already done so. Tell the veterinarian if your dog has ever been pregnant, how many puppies she had and whether they were all healthy, how long ago it was, and whether there were any complications. The more information your veterinarian has, the better because it helps with the diagnosis. The veterinarian will check your dog’s body temperature, blood pressure, heart and respiration rate, weight, and reflexes. He will palpate her abdominal area and give her a vaginal examination.

A urinalysis, vaginal swab culture, complete blood count (CBC), biochemical profile, electrolyte level test, and fecal examination will be done. The veterinarian will also Take radiographs (x-rays) of the abdomen and chest, CT scan, and possibly an MRI. He may decide to order an ultrasound as well to see the inside of your dog’s uterus in real time to look for any abnormalities in the blood flow. A sample of cells from the tumor will be taken with a small needle in order to test it for cancer. If it is not possible to get a sample with a needle biopsy, the veterinarian may decide to surgically remove the tumor for biopsy. This will help determine whether it is necessary for further treatment, such as chemotherapy.

The best treatment is to surgically spay your dog by removing the uterus and ovaries, and removal of any tumors that have metastasized to other parts of the body. The veterinarian will also remove any lymph nodes in the area that he thinks may be at risk of becoming cancerous. In addition, if the doctor feels it is necessary, chemotherapy treatments will be done before or after the surgery. Some of the most effective chemotherapy drugs used include carboplatin, cisplatin, and doxorubicin. In some cases, radiation treatments may also be done, but this kind of tumor does not usually respond well to radiation, so this is a last resort.

The average survival time for dogs with leiomyosarcoma that has been removed is about one to three years. You will need to bring your dog back to the clinic for visits every few months to get bloodwork and imaging to check for recurring cancer. If your dog was diagnosed with leiomyomas and had her uterus and ovaries removed she can be expected to live her life as if nothing happened. Be sure to keep regular appointments with your veterinarian to maintain good health for your dog.