Managing oral tumors (Proceedings)

Management of Oral Tumors

Oral tumors occur frequently in dogs and cats. Oral tumors account for approximately 6% of all malignant tumors in dogs with malignant cancer of the mouth and pharynx occurring 2.6 times more frequently in dogs than cats. Oral tumors can be benign or malignant. Unfortunately diagnosis of oral malignancies frequently occurs when the tumor is quite advanced necessitating more extensive treatment. Early diagnosis of oral tumors, appropriate staging, wide surgical resection and alternative treatment modalities can improve survival time.

Diagnosis of Oral Tumors

The diagnosis of oral tumors is based on biopsy of tissue followed by histopathologic examination. Small tumors or pedunculated lesions that can be resected with a gingivectomy may be primarily resected. Attempts to remove large oral masses with excisional biopsies are not recommended until a histopathologic diagnosis is available for surgical treatment planning.

Biopsy of large oral masses must be deep, because superficial biopsies may reveal only inflammation or gingival hyperplasia. A deep wedge biopsy or a deep Tru-cut is recommended. The use of electrosurgery for obtaining oral tumor biopsies is not recommended.

Clinical Staging of Oral Tumors

Following the histological diagnosis of oral malignancy clinical staging should include a complete blood count, serum biochemistry profile, urinalysis, fine needle aspirates of regional lymph nodes, and thoracic and skull radiographs. When available, advanced imaging techniques such as computed tomography and magnetic resonance imaging provide a more precise

An overview of feline oral squamous cell carcinoma (SCC) was recently published and included a review of the following: biologic behavior, pathology of SCC, diagnosis and staging, differential diagnosis, treatment options and prognosis.1 In summary this article reports that: oral SCC is a common malignancy in cats and responds poorly to treatment and that the mainstay of treatment is early diagnosis by use of oral examination, radiographic evaluation including advanced imaging techniques, biopsy and radical surgical excision.1 Recurrence despite aggressive surgical resection is common, thus multimodality therapy appears indicated.1 To date, cats that have been treated with mandibulectomy and curative-intent radiation post-operatively have had the longest survival times, however mandibulectomy has a high level of associated morbidity, but overall quality of life of the patients was felt to be good by most owners.

A wide variety of tongue lesions occur in dogs including: traumatic tongue lesions including severe multiple lacerations and tongue avulsions, foreign body granulomas, sublingual and buccal mucosal hyperplasia, lingual tumors, and glossitis secondary to chemical or immune-mediated diseases. A biopsy is often required to achieve a definitive diagnosis. Fine-needle aspirates and/or impression smears with cytologic evaluation along with gross evaluation of the lesion are often helpful in formulating a tentative plan. The most common malignant lingual tumor in dogs is the squamous cell carcinoma (SCC). Partial glossectomy is recommended for the treatment of lingual SCC in dogs when possible. In the past major resections of the tongue have not been commonly performed in animals because of concerns regarding unfavorable postoperative effects of diminished lingual function. A previous report in which major glossectomies were performed in five dogs demonstrated that glossectomies were well tolerated by dogs and that it may be a viable treatment option for aggressive tongue tumors and other conditions such as severe trauma or tongue avulsions that render the tongue unsalvageable. A classification system for glossectomies in humans have been applied for classification of major glossectomies in dogs. This classification system is divided into partial, subtotal, near total, and total glossectomies. A partial glossectomy is defined as excision or amputation of any portion or all of the oral (free) tongue rostral to the frenulum. A subtotal glossectomy involves the entire free tongue and a portion of the genioglossus, the geniohyoid muscles, or both, caudal to the frenulum. A near total glossectomy refers to resection of ≥ 75% of the entire tongue while amputation or excision of the entire tongue is defined as a total glossectomy. Two dogs in this study were successfully treated for total or complete avulsions of the tongue secondary to their tongues being entrapped in paper shredders with closure of the mucosa and placement of PEG tubes.

Surgical Treatment of Malignant Oral Tumors

Numerous mandibulectomy and maxillectomy procedures have been utilized in the surgical management of malignant oral tumors. The different types of partial mandibulectomy procedures include: rostral, hemirostral, hemicentral, total, caudal three quarter, and hemicentral/rostral mandibulectomy. The different types of partial maxillectomy procedures include: hemirostral, rostral, total hemimaxillectomy, central hemimaxillectomy and caudal hemimacillectomy. Regardless of the procedure performed, several surgical principles are recommended when performing partial mandibulectomies and maxillectomies including the following:

• Sharp dissection rather than electrocautery should be utilized when incising the labial, buccal, and palatal mucosa to minimize postoperative dehiscence.

• An adequate blood supply should be maintained to the mucosal flap that will be utilized to cover the oronasal or oroantral defect that results from the surgical procedure.

• A two-layer closure should be utilized when possible.

• Tissue tensions should be avoided across the incision line

• A one to two centimeter margin of healthy tissue should be removed with the tumor.

• The surgical specimen may be radiographed postoperatively

• The margins of the surgical specimen should be marked and submitted for histopathologic examination.

It is extremely important to carefully assess the surgical margins following mandibulectomy and maxillectomy procedures that have been performed for the treatment of malignant oral tumors. Evaluation of marking materials for cutaneous surgical margins has been previously described. Similar techniques can be applied for marking surgical specimens following mandibulectomy and maxillectomy procedures. The information obtained following evaluation of surgical margins by the pathologist will help the surgeon and oncologist with future treatment planning.

Lingual Tumors

Partial glossectomy may be necessary in dogs with extensive tongue trauma or tongue tumors. The most common malignant tongue tumor in dogs is a squamous cell carcinoma. A previous report in which major partial glossectomies were performed in five dogs demonstrated that major partial glossectomies were well tolerated by dogs and partial glossectomies may be viable treatment options for aggressive tongue tumors and other conditions that render the tongue unsalvageable. Performance of a partial glossectomy involves amputation of the tongue caudal to the lesion and in the cases of lingual squamous cell carcinomas up to 2cm caudal to the lesion to help insure clean surgical margins. To perform a partial glossectomy a surgical marker is used to mark the proposed glossectomy site. A Doyen clamp may be placed cranial to the resection site to help prevent backbleeding during the surgical procedure. The amputation is begun on one side of the tongue and vessels are ligated as they are encountered advancing the incision across the tongue while closing the suture site intermittently. The mucosa of the dorsal aspect of the tongue is sutured to the mucosa of the ventral aspect of the tongue in a simple interrupted pattern. Adjunctive therapy should be considered in these cases because of the possibility of lymphatic and vascular invasion associated with lingual squamous cell carcinomas.

Non-Neoplastic Oral Lesions

Non-neoplastic oral lesions occur frequently in the dog and cat. These lesions include: gingival hyperplasia, granulatomous reaction, eosinophilic granulomas, nasopharyngeal polyps, ophthalmic changes associated with retrobulbar lesions, lymphocytic plasmacytic stomatitis, feline mandibular swelling and osteomyelitis.

Sublingual and Buccal Mucosal Hyperplasia

Sublingual and buccal mucosal areas of excessively loose mucosal folds that are indurated and hyperplastic secondary to repeated self-inflicted trauma have also been described as "gum-chewers lesions" because the behavior of dogs with these lesions may mimic that of a person aggressively chewing gum. These lesions may become quite large and may be painful when they are repeatedly traumatized by chewing on the lesions with the molar teeth. When these lesions become ulcerated and become a source of pain for the patient surgical excision is recommended. The resected tissue should be submitted for histopathologic evaluation to rule out the presence of neoplasia.

Ophthalmic Changes Associated with Retrobulbar Swelling

Ophthalmic changes may be associated with oral tumors or dental disease of the maxillary 4th premolar, and the first and second maxillary molars. Some ophthalmic changes that may be associated with periodontal and endodontic disease include retrobulbar, orbital, periorbital, and conjunctival changes. Biopsy of the retrobulbar space may be necessary in cases in which the exophthalmus may be associated with a neoplastic process in the retrobulbar region.

Lymphocytic Plasmacytic Stomatitis

Cats with lymphocytic plasmacytic stomatitis (LPS) typically present with a history of halitosis, ptyalism, dysphagia, inappetence and weight loss. Oral examination reveals a hyperemic, proliferative ulcerative mucosa with a raspberry red, cobblestone appearance. These lesions may be primarily around the dentition but may extend onto the palatoglossal folds and fauces. The etiology is unknown. Histologically, this condition is characterized by infiltration of affected tissue with large numbers of lymphocytes and plasmacytes. The serum proteins are high because of severe elevations in the globulins.

Feline Mandibular Swelling

Feline mandibular swelling is not readily recognized become of the ventral location of the mandible. Without careful palpation of the ventral aspect of the mandible, mandibular swelling may not be detected. Feline mandibular swelling may be benign or malignant. The most common cause of benign mandibular swelling in cats is osteomyelitis secondary to retained odontoclastic resorptive tooth roots and less frequently secondary to periodontal disease and endodontic disease. The most common cause of malignant feline mandibular swelling is squamous cell carcinoma and less frequently fibrosarcoma, lymphosarcoma, and osteosarcoma. Thorough oral examination, dental radiography, and intraoral incisional biopsy will help provide a definitive diagnosis.

Osteomyelitis and Bone Sequestra

Osteomyelitis and bone sequestra are infrequently diagnosed in the oral cavity. Osteomyelitis and bone sequestra may be a complication of severe periodontal disease, extractions, or jaw fractures. Osteomyelitis or bone sequestra following extractions and jaw fractures may be caused by retained tooth roots, exposed alveolar bone, or operator-induced osseous necrosis. Bone sequestra may develop when a piece of alveolar bone is fractured off during a dental extraction and left in the extraction site. Several cases of severe osteomyelitis with secondary necrosis of bone have occurred in Cocker Spaniels and may be related to an inappropriate immune response in this breed. Dogs with osteomyelitis or bone sequestra are usually examined because of fetid breath, severe oral pain, facial swelling, reluctance or inability to eat and have severe purulent nasal discharge if the osteomyelitis or bone sequestra is located in the maxilla. Dental radiographic examination is performed to assist in the diagnosis. Teeth in the necrotic bone or retained tooth roots and boney sequestra are removed and necrotic bone curettaged to the level of healthy, bleeding bone. Intraoperative bacterial culture and sensitivity testing is performed. Tissue is submitted for histopathologic examination to rule out underlying neoplasia. The area is liberally flushed with sterile saline solution and closed with a mucoperiosteal flap. Broad-spectrum antibiotic therapy is initiated until bacterial culture and sensitivity results are available.

Feline Perialveolar Osteitis

A severe firm swelling around the root of the maxillary canine tooth may occur in middle-aged and geriatric cats. This bulbous maxillary canine tooth perialveolar swelling often occurs bilaterally and may be associated with periodontal or endodontic disease and should not be mistaken for neoplasia. Periodontal probing and dental exploration of the affected maxillary canine teeth often reveals a deep periodontal pocket or chronic pulpal exposure. A dental radiograph may reveal loss of trabecular bone pattern around the roots of affected maxillary canine teeth with a thin line of sclerotic bone surrounding the periradicular bone loss.

Dentigerous Cysts

Dentigerous cysts occur infrequently in dogs, however, the diagnosis of dentigerous cysts should be a primary consideration in young dogs presenting with oral swellings in edentulous areas. Definitive diagnosis of a dentigerous cyst is based on history, physical examination, dental radiography, and histopathologic examination. Dentigerous cysts arise from the cellular components of the developing dental follicle. The cyst contains one or more embedded teeth and usually surrounds the coronal aspect of the tooth. As the tooth bud continues to develop but fails to erupt, the cyst becomes filled with fluid. Fluid pressure within the cyst results in a smooth-bordered radiolucent cavity typically adjacent to the cementoenamel junction as viewed radiographically. The treatment of a dentigerous cyst usually involves surgical extraction of the affected tooth and thorough removal of the entire epithelial lining of the cyst wall which is submitted for histopathologic examination. Complete excision of the tooth and the cystic epithelium is curative.

References

Marretta JJ, Garrett LD, Manfra Marretta S. Feline oral squamous cell carcinoma: An overview. Veterinary Medicine 2007;102(6):392-410.

Dvorak LD, Beaver DP, Ellison GW, Bellah JR, Mann FA, Henry CJ. Major glossectomy in dogs: A case series and proposed classification system. J Am Anim Hosp Assoc 2004;40:331-337.

Manfra Marretta S. Management of maxillofacial osteonecrosis. In: Veterinary Oral and Maxillofacial Surgery, eds. Verstraete FJM, Lommer MJ, accepted 2008.

Manfra Marretta S. Maxillofacial surgery. Vet Clin North Amer (Small Anim Pract) 1998; 28(5):1285-1296.