Oral tumors account for 6 percent of all neoplasia in dogs1 and 10 percent of all neoplasia in cats.2 The practitioner and staff in general practice are on the frontline of diagnosis of oral tumors, and early detection is imperative. Here are eight tips for treating oral tumors in your practice, from initial presentation to definitive treatment.
Radiograph showing left total and right partial mandibulectomy in a cat with squamous cell carcinoma presenting to the Dentistry and Oral Surgery Service of the University of Pennsylvania. This cat is still alive five years after surgery. (Photos copyright University of Pennsylvania)
Oral tumors are not necessarily a death sentence.
The majority of oral tumors in dogs are benign. Even the dreaded canine oral melanoma shows variability in its likelihood to metastasize. A recent manuscript found a median survival time of almost three years with small, well-differentiated oral melanomas (most were less than 1 cm) that were excised without any further radiation, chemotherapy or immunotherapy.3 Even with larger melanomas, immunotherapy has shown promise in decreasing the chances of death from metastasis.4 Though the majority of oral tumors in cats are malignant, some cats with oral squamous cell carcinoma can be cured through surgery (see photos), depending on the tumor location and size.
- Stage the patient appropriately.
Chest radiographs are important in providing information of thoracic metastasis before further workup. Palpation of lymph nodes can be misleading, with 30 percent of metastatic lymph nodes being normal in size.5 Mandibular lymph nodes will tell some of the story, but other lymph centers exist, including the parotid and retropharyngeal. One study showed that only 54.5% of metastases will be found if histopathology is performed only on the mandibular nodes.6 Removal of all three lymph centers through a single incision has been described.7 Aspiration of nodes generally provides good sensitivity and specificity.8 Due to the fact that other lymph centers drain to the medial retropharyngeal node, this may be the most important lymph node to include when assessing for node metastasis. Aspiration of the medial retropharyngeal lymph node of the dog is possible in the hands of an experienced ultrasonographer.
- Utilize dental radiography and other diagnostics to assess extent of the oral tumor.
Much of the mandible or maxilla can be visualized when using size 4 dental X-ray films, providing a good estimation of margins for mandibulectomy procedures. Exceptions that require more advanced diagnostics (such as CT scan) include caudal mandibular tumors and all maxillary tumors since these can often be the “tip of the iceburg.”
Appearance of the same patient one year after surgery. The patient can eat and drink independently, but grooming is inefficient, necessitating frequent brushing or clipping of matted hair. (Photos copyright University of Pennsylvania)
Learn how to take a good incisional biopsy to obtain a diagnosis.
First, do no harm. The first tenet in obtaining a diagnosis is to avoid seeding tumor cells into areas that won’t be removed by the subsequent excisional surgery. The second tenet is to provide the pathologist with a helpful piece of tissue. This means avoiding inflamed, infected areas if possible. If mucosa is intact over a large oral tumor, it may be beneficial to make a semilunar incision into the mucosa, slightly elevate the mucosa, obtain a sample with a 15 blade or punch biopsy, and close the mucosa with a simple interrupted pattern. This will minimize bleeding of the biopsy site while awaiting the results of the biopsy prior to definitive treatment. Take enough tissue to ensure a diagnosis (which may mean both bone and soft tissue), and send the samples to a pathologist familiar with oral oncology. Pitfalls such as the histologically low grade, biologically high grade fibrosarcoma exist in the oral cavity.9 If the results of the biopsy and the clinical behavior of the tumor do not match, speak with your pathologist to consider if you may be dealing with a “high-low” fibrosarcoma. These tumors are easier to treat when they are small in size, so early detective work can save a life.
- Surgeons are only as good as their tools.
Siegel scalpel blade handles work well when obtaining biopsies due to their cylindrical shape for easy maneuvering of a 15 blade. Mandibulectomies and maxillectomies are dichotomous surgeries. The first part of the surgery involves transecting normal soft tissue structures to clear a path for osteotomy, followed by removal of bone and soft tissue to obtain tumor-free margins. The second half of the surgery is where finesse is necessary to attempt to reconstruct the remaining tissue to allow for the most aesthetic and functional reconstruction of the patient. Tools that make these goals easier include high-quality Metzenbaum or Ragnell scissors, Mixter or Dandy hemostatic forceps for easier ligature placement in difficult areas, and comfortable, high-quality needle holders since closure of an involved mandibulectomy or maxillectomy may require more than 100 simple interrupted sutures. Osteotomy can be done with a mallet and osteotome, but high-speed drills and sagittal saws provide greater control. Lasers or electrocautery can potentially help to provide an extra millimeter or two of deep margin by ablating the surface of the excised area, but avoid these tools when obtaining small incisional biopsies because thermal damage may preclude a diagnosis by the pathologist. Similarly, it may be difficult for a pathologist to comment on margins if these tools are used to excise a tumor. Since maxillectomy sites have potential for dehiscence (between 7 and 33 percent dehiscence rate10), I do not recommend cautery or laser use near mucosal cut surfaces to avoid thermal damage of the healing mucosa. Defects are closed with two-layer closure whenever possible, which sometimes necessitates drilling small holes in remaining bone to place sutures into the bone to tack down mucosal flaps. Closure of maxillectomy sites should be over supporting bone whenever possible.
- Anesthesia monitoring is important.
Oral surgical procedures, especially mandibulectomies and maxillectomies, take time. It is important to have access to top-notch monitoring equipment and to be prepared for possible sequela such as the need for intraoperative and postoperative blood transfusion.
- Debulking of oral tumors is largely unrewarding.
Fibromatous and ossifying epulides (now referred to as peripheral odontogenic fibromas) may be slow to recur if removed at their base, but because these tumors arise from the periodontal ligament, they will recur without removal of the tooth and periodontal ligament from which they arise. Larger and more vascular tumors are rarely amenable to debulking because often the cut surface of the debulked area will not regain epithelial coverage. Bleeding and secondary bacterial infections can adversely affect quality of life shortly after debulking.
- Patients, especially dogs, tolerate radical oral surgery amazingly well.
Dogs are usually eating within 24 to 48 hours after radical mandibulectomies or maxillectomies and will functionally adapt to their new situation fairly rapidly. Cats can be slower to rebound, and one manuscript found that 12 percent of cats never regained the ability to eat after mandibulectomy.11 Temporary esophagostomy tube placement should be part of mandibulectomy or maxillectomy procedures in the cat. Clients should be shown pre- and postoperative photos of other patients who have had similar surgeries. If aesthetics are an insurmountable concern for the client, or if margins are unlikely to be obtained by surgery, some oral tumors respond nicely to radiation therapy.
Dr. Lewis is assistant professor of dentistry and oral surgery at the University of Pennsylvania’s School of Veterinary Medicine.
3. Esplin DG. Survival of dogs following surgical excision of histologically
well-differentiated melanocytic neoplasms of the mucous membranes of the lips and
oral cavity. Vet Pathol 2008;45(6):889-96.
4. Bergman PJ, McKnight J, et al. Long-term survival of dogs with advanced malignant melanoma after DNA vaccination with xenogeneic human tyrosinase: a phase I trial. Clin Cancer Res 2003;9(4):1284-90.
8. Langenbach A, McManus PM, et al. Sensitivity and specificity of methods of assessing the regional lymph nodes for evidence of metastasis in dogs and cats with solid tumors. JAVMA 2001;218:1424-1428.
Oral tumors account for 6 percent of all neoplasia in dogs1 and 10 percent of all neoplasia in cats.2 The practitioner and staff in general practice are on the frontline of diagnosis of oral tumors, and early detection is imperative. Oral tumors account for 6 percent of all neoplasia in dogs1 and 10 percent of all neoplasia in cats.2 The practitioner and staff in general practice are on the frontline of diagnosis of oral tumors, and early detection is imperative. oral tumors, mandibulectomy, melanomas, mucosa, biopsy, mandibular, mandibulectomies, maxillectomies