Treatment Options for Possible Acanthomatous Epulis Tumor and Pleural Effusion

Lili Duda, VMD
Last Modified: November 1, 2001

Dear OncoLink "Ask the Experts,"
Last year you answered a question regarding our 10-year-old setter male neutered dog regarding his diagnosis of a recurring Acanthomatous Epulis tumor in his mouth. In January of 1999, he had a rostral mandibulectomy performed. The pathology report after surgery showed clear margins.

He was doing just fine when he developed a cough earlier this year and then problems with vomiting. He has undergone many tests and it has been determined by fluid drawn from his lung cavity that he has a malignant tumor of epithelial origin. They also stated that it could be a primary or metastatic carcinoma or possibly a malignant mesothelioma.

After a long series of tests we still are not sure where the primary cancer may be or which of the above cancers it could be. Since the report states that it is of epithelial origin we are curious as to what the term "epithelial origin" means.

Is it possible that the Acanthomatous Epulis could have been the originating cause of this new cancer? Could the Acanthomatous Epulis tumor have been malignant and not show up at the time of biopsy and removal? Any clarification could help greatly.

We are also told there is no treatment for these types of cancers—any comments—help or direction would be appreciated.  
Again Clancy's family thanks you.
P & S

Lili Duda, VMD, Editor of the OncoLink Veterinary Oncology Section, responds:

Dear P & S:
Acanthomatous epulis does not metastasize. There is a small possibility that the tumor diagnosed was actually something else, such as a squamous cell carcinoma, which does have some potential to metastasize. However, there are several reasons why this might not be the case. First, if I recall correctly, your dog Clancy had a recurrent tumor, and it was diagnosed as an acanthomatous epulis each time. Second, it has been almost two years since the primary tumor was removed, and in most cases metastasis would have shown up within the first year. Third, for a carcinoma of the head and neck, there is usually lymph node metastasis before or at the same time as lung metastasis.

Tumors fall into three basic types (please see article on Cancer terminology and symptoms).

  • Epithelial, which are tumors that arise from the surface, lining, and glandular tissues of the body (skin, intestinal tract, any glands, gum and oral mucosa, etc.).

  • Sarcomas arise from the connective and supportive structural tissues of the body (bone, cartilage, fibrous connective tissue, etc.).  
  • Round cell tumors include everything else (such as cancer of the blood cells, melanomas, etc.).
As far as your dog's current problem—it sounds like it may be a "pleural effusion" which is an accumulation of fluid between the chest wall and the lungs. There are a variety of causes for fluid accumulation, such as (but not limited to) heart disease, liver failure, and cancer. If it is cancer, it can be a primary lung tumor, which might be visible with ultrasound if fluid is present in the chest, on a chest X-ray once the fluid has been drained from the chest cavity, or on a CT scan. It might be metastasis to either the lung tissue itself, or the lining of the chest cavity. In this case we look for the primary tumor everywhere in the body, but sometimes even with a thorough search it can't be found. Mesothelioma is a rare cancer in dogs arising directly from the lining of the chest cavity. It can be difficult to diagnose on fluid evaluation alone, and sometimes a biopsy of the tissue itself is required.

Treatment of a malignant pleural effusion (that is, fluid accumulation due to cancer) depends to a large extent on the tumor type. However, in most cases the prognosis is not good and treatment is considered strictly palliative. Systemic chemotherapy might help decrease the tumor burden and thereby slow down fluid accumulation. Intracavitary chemotherapy, in which chemotherapy is placed directly into the chest cavity, has been reported to help dogs with some types of tumors. Surgery to remove the cancer is only an option if a single mass is responsible for the symptoms, and is unlikely to be curative.

The side effects and costs (both financial and time investment) of treatment options must be balanced against the likelihood of success and expected duration of response. This analysis will be very dependent on each specific dog, veterinarian, and owner.

I wish you the best of luck with Clancy.