Nerve Sheath Tumor in Dogs

Nerve Sheath Tumor in Dogs is an abnormal growth or mass of the skin and soft tissue. The tumor is comprised of Schwann cells that are found in connective tissue known as the myelin, or cover, that surrounds the nerve. Myelin acts as insulation and a conduit for the transmission of nerve signals. Nerve sheath tumors are firm, white nodules beneath the skin that can be attached to peripheral as well as central nerve tissue. The tumors can remain unseen and will effect any location in the nervous system.

Symptoms tend to be site-specific and include the following:

• Ataxia (lack of muscle control)
• Atrophy
• Difficulty walking
• Horner’s Syndrome (drooping eye due to compression on ocular nerves)
• Limb weakness
• Pain
• Swelling

Types

There are two main types of nerve sheath tumors: neurofibromas/Schwannomas and neurofibrosarcomas/malignant Schwannomas.

• Neurofibromas/Schwannomas are benign (non-cancerous)
• Neurofibrosarcomas/malignant Schwannomas are malignant (cancerous)

Both types need to be evaluated and removed surgically to decrease discomfort and the likelihood of the tumor to develop further or increase in size. Generally, this type of tumor does not metastasize (spread to other locations throughout the body). The malignant tumors are characterized by having the potential to become invasive and grow rapidly.

There is no publicly disclosed cause at this time. The average age of onset for most breeds is 9. There is a higher chance of the following breeds to be affected:

• 16% Golden Retriever
• 12% mixed breeds
• 10% Labrador Retriever
• 9% Boxer
• 6% Collie

Diagnosis can be performed by the veterinarian in a manner of different ways. Tissue biopsy, either by removing a small portion surgically, or aspiring a sample with a needle is the main mode of discovery. The veterinarian may also choose to perform a CT scan and/or X-Ray to help determine if the tumor has become invasive. Depending on how long the dog has shown symptoms and how severe they are, the veterinarian will decide at that time how many tests need to be performed. Once it is determined if the tumor is benign or malignant, excision of the affected tissue will be performed.

Surgery

All tumors will be removed whether they are benign or malignant. Advantages to removing a tumor that is benign are that the tissue can be further tested to determine what cells it was made up of, and the dog will be more comfortable without the added pressure of the extra tissue. Benign tumors will also be sent for more in-depth histological testing. It is important for the veterinarian to try to remove all of the involved tissue, as even a small amount left behind can re-grow into another tumor that will need further attention.

Radiation Therapy

If the tumor was found to be malignant, radiation therapy is a possible treatment the veterinarian may suggest. This therapy works by stopping the division of cells at the site of the tumor to deter further growth. The treatments last 3-4 weeks. Due to technological advances over the years, most dogs do very well with this procedure, and it has a real success rate in deterring the growth of future tumors. Side effects are minimal and may include temporary or permanent hair loss at the site of treatment.

Chemotherapy

The veterinarian may decide your dog would also benefit from chemotherapy treatment to increase the likelihood of cancer-free time. Chemotherapy is a chemical agent that stops cells from dividing as well. Unlike radiation, which is centered directly at the site of the cancer, chemotherapy treats the entire body. The administration methods include subcutaneous, (under the skin) intramuscular, intravenous, or oral. Dogs respond very well to chemotherapy and have little to no side effects.

If your dog’s tumor was benign, the recovery and management is quite like that of any other daily routine with your dog. All steps should be taken to make sure your pet is safe and comfortable after surgery by adhering to any take-home outpatient instructions. It will be critical of you (the owner) to continue to monitor the site for proper healing and any signs of a returned tumor. If your dog’s tumor was malignant, the above instructions apply, as well as making sure all of the follow-up treatment appointments are met. Proper nutrition is extra important at this time to make sure all surgical wounds heal well, and your dog has the vitamins and minerals needed to regain and maintain their strength. If the surgical site becomes red, swollen, painful, or shows signs of infection or tumor regrowth, it is imperative to return to the veterinarian for further evaluation.

The best form of treatment is to remove all the tumors regardless of whether or not they are benign or malignant. This, of course, means that surgery is required. This surgery can cost $1,500 or more depending on the severity of your dog’s condition. However, once all of the tumors are removed your dog will be much more comfortable. If the tumors have remained localized and are determined to be malignant then the veterinarian will most likely want to administer radiation therapy. Your dog’s hair may fall out at the radiation site as a side effect. Radiation therapy generally costs between $2,000 and $7,000. Unfortunately, if the tumors have begun to spread to other parts of the body then the veterinarian will recommend chemotherapy. Chemotherapy treats the whole body rather than a localized point. This is an option with little to no side effects for your dog and can be administered in a variety of ways.