Rhabdomyosarcoma in Dogs

Studies show that large, deep, fast growing rhabdomyosarcoma tumors tend to be malignant. They can metastasize in organs such as the liver, kidney, spleen, adrenal glands and lungs. While there is no sex predisposition to soft tissue cancer in canines, rhabdomyosarcomas have been found in both younger and older dogs, and most commonly in medium to large breed canines. Early diagnosis is key to the prognosis; therefore, it is recommended that any visible growth or lump you may discover on your dog be checked immediately.

Tumors of the soft tissue, specifically the rhabdomyosarcomas in dogs, are masses that arise in skeletal muscles. A relatively rare tumor, the rhabdomyosarcoma growth can quickly increase in size and has the capability to metastasize rapidly if malignant. If you see a lump or mass on your pet, visit your veterinarian for a consultation without delay.

As with many types of cancer, the presence of the disease is not always apparent. A growth of any kind should be investigated as soon as possible, in order to avoid the serious consequences and extensive treatment that cancer can bring.

• Lesions or masses will be present
• Swelling may be obvious
• The masses are often firm and in a fixed position
• The tumor may appear to be localized but can become invasive to the surrounding tissue
• They can evolve into ulcerated, infected tissue
• Tumors are common on the trunk, extremities, and oral cavities
• Symptoms for rhabdomyosarcoma can vary depending upon location
• Cancer of the larynx, for example, will exhibit symptoms such as difficulty breathing or loss of bark
• An oral mass may show signs of halitosis (bad breath) or excess salivation
• A tumor of the limb will produce lameness
• Bladder masses may cause blood in the urine (hematuria)

Types

There are four main classifications of rhabdomyosarcomas in canines.

• Embryonal
• This is the most common form found in dogs
• Older breeds are mainly affected
• Tumors can be found in the trachea and heart muscle, among other locations
• They are found most often in young canines
• Pleomorphic
• Pale, white, or tan masses appear
• These tumors can cause cancer to spread to the organs
• Botryoid
• This is a rare form of rhabdomyosarcoma that is grapelike in appearance
• The average age of dog with this form of cancer is 1.5 years, and large breeds are also predisposed
• It is usually found in the bladder
• Alveolar
• The abdomen, jaws, and face are locations where the mass commonly forms
• Tissue death and hemorrhage will most likely occur

As we find in the medical documentation for cancer in humans, the cause of some cancers is not specifically defined. Your furry family member may have developed a soft tissue cancer due to the factors listed here.

• Trauma
• Parasites (Spirocerca lupi)
• Foreign bodies
• Radiation
• Orthopedic implants

The veterinary team at the clinic will perform a physical examination as the diagnostic process begins. No doubt, you will be able to point out the location of the mass you are concerned about. Because your veterinary caregiver has experience with scrutinizing the canine body form, she may find lesions or tumors that you did not know were present.

When a tumor is located, your veterinarian could assess the tumor size and scale of fixation simply by palpating the lump. In the case of an oral or bladder tumor, further testing methods are necessary for determining the presence and type of tumor.

Tools that may be used are listed here.

• A fine needle aspirate is a noninvasive microscopic evaluation that can explore the possibility that the lesion is a cyst
• A biopsy of tissue will determine the type of rhabdomyosarcoma present
• A 3 view radiograph of the thoracic area may determine the stage of the disease
• Abdominal ultrasound can further evaluate the lymph node involvement
• A computerized tomographic scan and a magnetic resonance imaging scan can provide additional important information about cancer, and will enhance the surgical plan if needed

Other tests will include complete blood count, serum biochemical profile, electrolyte panel and urinalysis.

Treatment for your beloved family pet will include surgical removal of the tumor (if possible). A thorough first removal surgery is ideal, in order to prevent recurrence. Your veterinary care team will carefully determine the scope of the surgical area. Soft tissue cancers tend to require a wide, deep incision in order to remove the entire tumor. Fortunately, for some canines, the removal of the lesion is the only treatment required.

Other pets will need accompanying radiation. This is often the protocol, to prevent or reduce the regrowth that may occur. Radiation is also used on tumors that are not able to be removed. Chemotherapy is an additional treatment step. It works best in combination with surgery and/or radiation but is sometimes used alone as a method of improving the quality of life and lifespan of a dog with an inoperable mass.

Limb amputation is another option for tumors of the extremities but is often not the preferred treatment if surgery is a viable choice.

The overall prognosis for your pet can vary depending on several factors.

• The behavior of the tumor will differ from canine to canine
• Whether the tumor has metastasized or not will be a factor
• The size and structure of the lesion will affect the success of a complete removal at first surgery
• Incomplete removal the first time will usually mean a second surgery, or a recurrence and then additional surgical needs
• Additional surgeries can mean an increase in the chance of morbidity, treatment cost and risk of recurrence
• Deep tumors are not easily removed and are often malignant
• Surgery, radiation, and chemotherapy will all involve subsequent follow-up, examination and testing, necessary to gauge the recovery process

This being said, your much-loved pet can have a successful surgery and recovery if the cancer is caught early and aggressive treatment begins soon after the diagnosis. Your veterinary team will be able to counsel you in the best course of action to take to give your appropriate pet care, whether in the form of tumor removal, amputation of a limb, or palliative treatment.