Giant Cell Tumors in Dogs

Giant cell tumors are a type of malignant fibrous histiocytoma that originates from more than one cell. These tumors typically do not metastasize, though they may spread to the spleen or other organs. Because the symptoms for malignant fibrous histiocytoma are nonspecific, it can be mistaken for other types of cancer, which is why a biopsy is necessary for a correct diagnosis.

The symptoms for giant cell tumors are nonspecific and include:

• Lethargy
• Depression
• Loss of appetite
• Vomiting
• Diarrhea

With most cases of malignant fibrous histiocytoma, the tumor is present as a detectable mass under the skin. These may appear anywhere on the dog’s body. Anemia or abdominal pain may also be present in dogs whose malignant fibrous histiocytoma have metastasized to the spleen.

Giant cell tumors occur in and beneath the skin and may spread to the spleen or other organs. There is no known cause for malignant fibrous histiocytoma though Golden Retrievers and Rottweilers seem to be predisposed to the condition. Older dogs are typically more at risk.

If you notice an abnormal mass beneath your dog’s skin, bring it to the veterinarian’s attention right away. As with most comprehensive examinations, the veterinarian will conduct a thorough physical examination and take down your dog’s history. During this initial examination, let the veterinarian know about any clinical signs you have observed, as well as their duration and severity.

The veterinarian will perform tests on your dog, which may include a complete blood count and a urinalysis. However, a diagnosis of a giant cell tumor is usually confirmed with a biopsy, which will show multinucleated giant cells in the tissue. Additional diagnostic tests, such as radiographs and ultrasounds, show the size of the tumor and reveal any metastasis if present. Though imaging may not differentiate malignant fibrous histiocytoma from other tumors, it provides a clearer idea of the extent of the condition, which allows for proper treatment.

Surgery is historically the treatment of choice for malignant fibrous histiocytoma, especially for cases in which the tumor has not metastasized. The goal is to eradicate the primary tumor completely before it can spread to the spleen or other areas of the body.

For cases in which the tumors have spread throughout the body or in which the dog is not otherwise a good candidate for surgery, chemotherapy may be used to control metastasis and to extend the dog’s life. However, chemotherapy will not remove the tumor or cure the disease, and the tumor may eventually lower your dog’s quality of life.

If your dog underwent surgery, you will need to provide a comfortable place to rest during the healing process. Your dog should be allowed to recover in peace and quiet. During this time, limit your dog’s physical activity, and ensure that he or she does not bite at the surgical site. An Elizabethan collar may be useful.

Whether your dog was treated surgically or with chemotherapy, you will need to follow up with the veterinarian periodically. The veterinarian will check to ensure that the tumor was eradicated entirely during surgery and that the malignant fibrous histiocytoma is not recurring. If you opted for chemotherapy, the drugs might need to be administered in the veterinary office, and the veterinarian will need to monitor the extent of the tumors.

In both cases, you should monitor your dog carefully and watch for additional clinical signs. Any changes in your dog’s behavior should be reported to the veterinarian.