Recognition and Treatment of Oral Tumors

Sandra Manfra Marretta, DVM, Diplomate, ACVS, AVDC
University of Illinois

Benign and malignant oral tumors occur frequently in small animals. Radiography and biopsy of oral lesions can assist in confirming a diagnosis. Surgical treatment of oral tumors may include mandibulectomy and maxillectomy techniques.

Clinical Signs

Oral tumors occur frequently in the dog and cat. The clinical signs that may be associated with oral tumors include: (1) slow progressive facial swelling, (2) nasal discharge, (3) abnormal salivation, (4) oral hemorrhage, (5) difficulty eating, and (6) loose teeth. A thorough evaluation of the patient will result in an accurate definitive diagnosis.

Preoperative Assessment

Prior to treating an animal suspected of having an oral tumor, a CBC and blood chemistry should be performed to reveal any concurrent disease. Thoracic radiographs should be taken to evaluate for the presence of pulmonary metastatic disease. A complete oral examination should be performed under general anesthesia and radiographs of the mandible or maxilla should be taken to help determine the extent of tumor involvement. Computed tomography when available is extremely accurate and helpful in localizing the full extent of tumor involvement. An incisional biopsy should be taken to confirm the diagnosis, aid in the rendering of an appropriate prognosis and provide a solid basis for a rational treatment protocol.

An informative biopsy can be obtained by the surgeon by avoiding biopsying areas of superficial necrosis but rather biopsying deeper more viable tissues. Electrocautery should be utilized to obtain small samples of tissue because this may result in a coagulated nondiagnostic sample. The biopsy should be taken with a #11 scalpel blade usually in the shape of a deep wedge. Following removal of the surgical biopsy the biopsy site may be closed with a horizontal mattress suture of 2-0 or 3-0 chromic catgut suture. If hemorrhage is brisk bleeding may be controlled with electrocautery but only after the biopsy has been removed from the surgical site. In cases in which submandibular lymph nodes are enlarged, a submandibular lymph node biopsy should be taken since these biopsies are helpful in staging the tumor.

Malignant Oral Tumors

Malignant oral tumors are frequently very aggressive. These tumors may spread by dirct extension and advance along tissue planes and potential spaces of the head and neck, or they may invade adjacent bony or cartilaginous tissue. The most common route of metastasis is by the lymphatics or by the blood to the regional lymph nodes and lungs. The probability of curing the patient and eradicating a malignant oral tumor decreases with extenion of the tumor from the primary site. Other factors that affect the prognosis of oral tumors include the anatomic site of the primary neoplasm, the metastatic pattern of the tumor, and the accessibility to the affected site for administration of therapy.

It has been previously reported that malignant oral neoplasms represent approximately 5.4% of all malignant cancers in dogs and 6.7% in cats. Benign tumors of the oral cavity are rare in the dog and cat. However, they may look grossly like malignant tumors. It is therefore important to plan therapy based on a histopathologic diagnosis and not on gross appearance of the tumor.

The three most common oral malignant tumors in the dog in decreasing order of incidence are the (1) melanoma, (2) squamous cell carcinoma, (3) fibrosarcoma. In the cat the most frequently reported malignant tumor by far is the squamous cell carcinoma. Cats rarely present with melanomas and fibrosarcomas occur at about the same frequency as in dogs.

Of all the oral neoplasms, the melanoma is the most aggressive. It may be pigmented or nonpigmented. Melanomas often ulcerate and bleed, they grow rapidly and they metastasize early to regional lymph nodes and lungs. Early surgical excision is the treatment of choice for oral malanomas. However, the prognosis is guarded because of its tendency toward early metastasis.

Squamous cell carcinoma is the most common oral tumor in the cat and is the second most common oral tumor in the dog. These tumors tend to be locally invasive, cause lysis of bone and may present with loose teeth. Oral squamous cell carcinoma in cats grow rapidly, ulcerate and become secondarily infected early in the course of the disease. These tumors tend to spread late in the course of the disease and are relatively sensitive to radiation therapy. The prognosis in dogs with oral squamous cell carcinomas if therapy is timely and correct is fair with approximately 50% of treated dogs living one year. The prognosis in cats with oral squamous cell carcinoma is very poor because of the rapid growth of this tumor in cats and the advanced stage of the disease these cats have at the time of initial clinical presentation.

Tonsillar carcinomas in dogs carry a very guarded prognosis. These tumors tend toward early metastasis to regional lymph nodes. These animals usually present with signs referable to orophayngeal obstruction including dyspnea, anorexia, coughing and drooling. The cervical swelling associated with regional lymph node metastasis can be misdiagnosed as a primary thyroid tumor or lymphosarcoma. Therefore, whenever a dog is presented with a firm, thick, ventral proximal semi-circular cervical swelling, thorough examination of the tonsils should be performed to reveal the possible presence of a primary tonsillar carcinoma.

Fibrosarcoma is the third most frequently diagnosed malignant tumor of the canine oral cavity. Although it is the second most frequently diagnosed malignant oral tumor in the cat it is still uncommon. Grossly fibrosarcomas are firm, red or pink, they are smooth and multilobuated. They tend to be locally invasive but rarely do they metastasize. Fibrosarcoma, though a localized disease, has a poor prognosis because it is locally aggressive, radio-resistant and the palatine location seen sometimes with this tumor makes surgical resection difficult.

There are three malignancies that clinically often occur as systemic diseases that may present with oral lesions and include mast cell tumor, lymphosarcoma, and hemangiosarcoma. These lesions should be biopsied and treated appropriately.

Benign Oral Tumors

The most commonly occurring benign oral tumor in the dog is an epulis. Epulides arise from the periodontal ligament. Canine epulides have been classified into three types: (1) fibromatous epulis, (2) ossifying epulis, and (3) acanthomatous epulis. All three types of epulides are benign; however, the acanthomatous epulis is a locally aggressive tumor and causes radiographic lysis of bone. Acanthomatous epulides are in the process of being reclassified as ameloblastomas. Ameloblastomas are tumors of the dental laminar epithelium. Treatment of fibromatous and ossifying epulides consists of local surgical resection of the tumor and gingival sulcus curettage. An acanthomatous epulis or ameloblastoma must be treated more aggressively to assure complete resection and prevent recurrence of the tumor and further destruction of bone. These tumors are sensitive to radiation, however, malignant transformation following irradiation has been reported.

Surgical Management of Oral Tumors

Early detection, diagnosis and treatment are essential in the management of oral tumors. Surgery is the most effective mode of therapy for treating most oral neoplasms. Surgical techniques utilized in treating malignant oral tumors include various types of partial mandibulectomies and maxillectomies depending on the location of the tumor. Several surgical principles should be utilized when performing these procedures and include the following: (1) Sharp dissection rather than electrocautery should be utilized when incising the labial, buccal, and palatal mucosa to minimize postoperative dehiscence, (2) 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, (3) A two-layer closure should be utilized when possible, (4) Tissue tension should be avoided across the incision line, (5) A one centimeter margin of healthy tissue should be removed with the tumor.

Following the establishment of at least a one centimeter border of normal healthy tissue between the tumor and the line of resection, the mucosa is incised around the tumor. The underlying bone is cut with an osteotome and mallet or an oscillating saw. Following removal of the surgical specimen it is submitted for histopathologic examination. The oral mucosa is closed with synthetic absorbable suture material using a simple interrupted pattern. Postoperative problems that may be associated with partial mandibulectomy and maxillectomy procedures include incisional dehiscence, infection, injury to salivary ducts, subcutaneous emphysema, mandibular instability, abnormal salivation with secondary cheilitis/dermatitis, anemia, pain and discomfort, lingual dysfunction and prehension difficulties, anorexia, ocular problems, cosmetic defects, local tumor recurrence, and distant metastatic disease. Appropriate presurgical planning and careful intraoperative technique can minimize these postoperative problems.

References

1.  Matthiesen DT, Manfra Marretta S: Results and complications associated with partial mandibulectomy and maxillectomy techniques. Prob Vet Med (Dentistry) 2:248-275, 1990.

2.  Manfra Marretta S, Matthiesen DT, Matus R, Patnaik A: Surgical management of oral neoplasia. In Bojrab MJ, Tholen M (eds.): Small Animal Oral Medicine and Surgery. Philadelphia, Lea & Febiger, 1990, 96-120.

3.  Harvey CE: Oral surgery. In Harvey CE (ed.): Veterinary Dentistry. WB Saunders 156-180.