Clinical Rounds: Battling a Labrador's oral malignant melanoma - Veterinary Medicine
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Clinical Rounds: Battling a Labrador's oral malignant melanoma
After a referring veterinarian diagnosed this deadly neoplasm in a senior Labrador retriever, this team of experts stepped in to help extend the dog's life with targeted treatment. What can you learn from their approach to help your patients?



Rachel Seibert, DVM

Rachel Seibert, DVM
The treatment of choice in dogs with oral malignant melanoma without distant metastasis is wide surgical excision with margins of at least 2 cm. Recurrence rates range from 15% to 22% in dogs that have undergone complete excision, while those that have undergone incomplete resection have a recurrence rate of up to 65%.12,13 Complete resection of most oral melanomas, with the exception of those confined to the lip margins or tongue, requires partial mandibulectomy or maxillectomy.

Hemorrhage is the main intraoperative complication, which typically occurs after the transection of the infraorbital, sphenopalatine, or major palatine artery during maxillectomy or the inferior alveolar artery during mandibulectomy. Excessive and potentially life-threatening bleeding may also occur because of disruption of nasal turbinates. Hemorrhage is typically controlled by pressure, vessel ligation, or, in severe cases, temporary carotid artery ligation.14

Mandibulectomies and maxillectomies are closed by suturing mucosa to mucosa in a simple interrupted or continuous pattern with absorbable monofilament suture material. If necessary, flaps may be developed to reduce tension.

Tumors ventral to the orbit may require transection of a portion of the zygomatic arch and the ventral aspect of the orbit, neither of which adds substantially to the overall morbidity.

Labial mucosa may be sutured to preplaced holes drilled in the hard palate to help prevent dehiscence, which is the most common postoperative complication.15 Dehiscence is most common after caudal or central maxillectomies requiring palatal flaps (with a reported incidence of 7% to 33%)4,13,16 and less common after bilateral rostral mandibulectomies when mucosal closure is directly over transected bone ends. Dehiscence can largely be avoided by preventing excessive tension during closure, although it is also associated with incomplete excision, tumor recurrence, exposed bone, excessive use of electrocoagulation, and infection. Often, dehiscence is minor and can be monitored and allowed to heal by second intention.

3. A dog two months after bilateral hemimandibulectomy for an oral tumor.
Other postoperative complications include hypersalivation, difficulty prehending, infection, mandibular drift, malocclusion, inadvertent trauma to tooth roots, subcutaneous emphysema, facial swelling, and oronasal fistula.17 The tongue may hang out from the mouth after hemimandibulectomy. A commissurorrhaphy (surgical closure of the lips further rostrally) may help prevent this.

Surprisingly, most dogs will eat after even radical maxillectomies, and feeding tubes are rarely required. Although the patient's appearance can be drastically altered, the postoperative cosmetic appearance is acceptable to most clients, with 85% of owners being satisfied with their decision to treat their dogs in one study (Figure 3).18


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