Oral pathology and anatomic abnormalities (Proceedings)

Introduction

This session will deal with the commonly seen neoplasms of the oral cavity and those conditions that look like tumors but arise from an outside source. Oral tumors arise from the gingiva, buccal mucosa, tongue, mandible, maxilla, palate, dental structures or tonsils.

Breed and species disposition

The oral cavity is the 4th most common site of malignant neoplasia in dogs and cats.1 The three most common oral tumors in dogs are malignant melanoma, nontonsillar squamous cell carcinoma and fibrosarcoma. Oral tumors occur 2.6 times more often in dogs than cats and 2.4 times more often in male dogs than females. 10% of all tumors in cats are seen in the oral cavity with 90% of those oral tumors being malignant. The age disposition for tumors of the oral cavity is commonly seen in geriatric patients with the exception of oral fibrosarcoma which can be seen in young large breed dogs. Common breed disposition for oral tumors is Cocker Spaniels, Poodles, German Shepherds, German Shorthaired Pointers, Weimaraners, Golden Retrievers, and Boxers.2

Clinical symptoms

Patients will present with the following symptoms: dysphagia, halitosis, hemorrhage, ptyalism, anorexia, sneezing, ocular or nasal discharge, pawing at the mouth, facial swelling, tooth displacement, thickening of the bone of the maxilla or mandible, exophthalmos and pain. In the case of malignant oral tumors, by the onset of clinical symptoms the stage of the tumor can be quite advanced.2

Neoplasms from trauma

Gum chewers syndrome

This syndrome is caused by mechanical trauma. The pet chews on the inside of its cheek or tongue. This causes a proliferative granulomatous hyperplasia to occur at the site. If the chewing is mild the damage will be low. In extreme cases, the lesions can become large, bleed regularly and cause pain.3

Neoplasms from infectious agents

Gingival hyperplasia

Gingival hyperplasia is a proliferation of the tissue of the attached gingiva. It may occur due to an inflammatory response such as dental plaque or calculus. The excessive gingival tissue can form what's called a "false pocket" – the extra tissue increases the depth of the sulcus. The hyperplastic tissue is usually benign. Treatment consists of treating the underlying periodontal disease and a gingivectomy to remove the excess tissue. This condition can be an inherited trait in certain breeds such as Boxers, Great Danes, Collies, Dobermans, and Dalmatians.4

Pyogenic granuloma

These lesions result from irritation of a specific site on the gingiva. The gingiva proliferates the area with granulation tissue. This irritation can be a foreign body or an infected wound. Removing the irritant will usually remove the lesion.4

Feline eosinophilic granuloma

These are chronic progressive lesions which involve not only the lips and the oral cavity, but the skin as well. It occurs most often in 3 year old spayed cats. The lesions are large, ulcerated, erythematous and raised. The causes have been anything from grooming to the idea that it is an immune mediated disease. However, this disease is contagious to other cats which suggest an infectious agent as the cause. A biopsy should be taken to rule out neoplasia or autoimmune disorder. Treatment consists of decreasing doses of steroids, but recurrence is common. Radiation and cryosurgery have yielded the best results.1,4

Chronic alveolar osteitis

This condition is commonly associated with the maxillary canines and seen most often in the cat. One can see a distinct bulging of the gingiva on the buccal aspect of the canine tooth. It can sometime involve the region of the mandibular symphysis. In most cases this arises as a result of chronic inflammation, usually periodontal disease. Periodontal pockets may be present. The periodontal disease should be treated appropriately, but the osseous changes are usually irreversible. If a tooth needs to be extracted, closing the extraction site may be tricky. Making releasing incisions, raising a periodontal flap and performing alveoloplasty to flatten the bulge will make the closure go more smoothly.3

Infectious papilloma

This is a viral disease usually seen in young dogs. It is caused by infection with a papovavirus. The lesions are usually white, smooth and slightly elevated. They are found around the lips and the tongue. The warts may come in singles or multiples and persist for 4-8 weeks. The warts undergo spontaneous remission or can be surgically removed in advanced cases.2,5

Oropharyngeal tumors

Epulides

Epulis is a clinically descriptive term. The term refers to any localized swelling on the gingiva. They tend to be rare in cats. Epulides contain dental lamina cells from the periodontal ligament or gingival epithelium. Historically, epulides have been divided into three types.6

Fibromatous epulis

This is the most common type. The lesions are usually smooth, pink and pedunculated. They do not invade bone.6

Ossifying epulis

This originates from the periodontal ligament/gingival epithelium. They are slow growing and calcified with a broader base of attachment. There are also strands of odontogenic material often present. There is a push to have fibromatous and ossifying epulides reclassified as peripheral odontogenic fibromas.6

Acanthomatous epulis

The acanthomatous epulis shows a biological behavior similar to intraosseous ameloblastoma in humans and recently the term canine acanthomatous ameloblastoma has been recommended. These can be locally aggressive, displace teeth and invade into bone. When the bone lysis is visible radiographically, a significant amount of the bone cortex has been destroyed. These tumors do not metastasize so a wide local incision is curative.5,6

Types of oral tumors

There are two classifications of tumors which are determined by their cell of origin. Nonodontogenic arise from structures of the oral cavity and odontogenic arise from the dental laminar epithelium.2 Oral tumors are generally locally aggressive with metastasis being infrequent. The exception to this is in the case of malignant melanoma, high grade sarcomas and tonsillar squamous cell carcinoma. Benign oral tumors have an excellent prognosis with treatment.2

Nonodontogenic tumors

Squamous cell carcinoma (SCC)

It is the most common oral neoplasia in dogs and cats. It is categorized as either tonsillar or nontonsillar depending on the location in the oral cavity. Tumors are pink in color, firm and irregular. In cats they may also have firm white nodules. In nontonsillar SCC the most common sites of involvement are the lips and tongue and have a tendency to grow rapidly, ulcerate and become secondarily infected. Nontonsillar SCC is locally invasive, rarely metastasizes and is radiation sensitive. Tonsillar SCC is more aggressive with metastasis possible to the regional lymph nodes and lungs and is radiation resistant. Prognosis is dependant on the stage and location of the tumor. Cats generally have a poor prognosis for long term survival.2,5

Malignant melanoma (MM)

Malignant melanoma is the most common tumor in dogs. They originate from the mucosal or gingival melanocytes. Tumors are generally found on the gingival, labial or buccal mucosa or the hard palate. They are locally invasive, either variably pigmented or amelanotic, ulcerated and necrotic; thus halitosis will be present. 50% of patients will have early metastasis. Prognosis is poor if the tumor has metastasized and guarded if it has not. Malignant melanoma is rare in cats.2

Fibrosarcoma (FSA)

Fibrosarcomas are the second most common malignant tumor in dogs and cats. They originate from the stroma of the gingiva or the soft palate, with the gingiva being the most common site of involvement. The average age of the patient is 8 years old in dogs and 10 years old in cats. The tumors are firm, flat, multilobulated and deeply attached to underlying tissue. Ulceration is not commonly seen. They respond poorly to radiation and chemotherapy. They can also recur after surgical excision. Prognosis is poor.2

Odontogenic tumors

Odontogenic tumors are unique to the jaw bone and teeth. The tumors originate from the tissues associated with tooth development. Knowledge of odontogenesis is helpful to better understand these tumors. The tumors are classified according to their tissue of origin. There are epithelial (ectodermal) odontogenic tumors that arise from the odontogenic epithelium. There is no hard tissue formation so they are also classified as noninductive. Connective tissue (mesodermal) odontogenic tumors arise from connective tissue elements. Mixed odontogenic tumors contain both epithelium and connective tissue. These tumors have hard tissue formation and are further classified as inductive.2,5,6

Ameloblastoma (epithelial odontogenic tumor, noninductive)

This is the most common odontogenic tumor. They are locally invasive, intraosseous tumors with histological similarities to the acanthomatous epulis. They cause osteolysis, so loose teeth are often seen. The tumors appear white to gray to pink in color. It is extremely rare for an ameloblastoma to metastasize. Treatment of choice is to remove the tumor with 1 cm of radiographically healthy bone on all margins.2,5,6

Odontoma (mixed odontogenic tumor, inductive)

The odontoma is an hamartomatous lesion (a tumor-like nodule composed of an overgrowth of mature cells or tissues normally present in the affected site but is disorganized) which contains all the tooth parts (enamel, dentin, cementum, pulp) in either recognizable tooth shapes (compound odontoma) or in a gnarled solid mass (complex odontoma). Radiographically, compound odontomas are unilocular with radiopaque structures that resemble miniature teeth or denticles. Complex odontomas show up as a solid radiopaque mass with a radiolucent band around it. Treatment of choice is enucleation of the mass from the surrounding bone. Odontomas have been diagnosed in young dogs, horses and cats.5,6

Diagnosis and treatment of oral neoplasms

The diagnosis and treatment plan for any oral neoplasm uses a combination of procedures. You must use a combination of thorough history taking, standard and dental radiography, CT scans, collecting good samples and submitting them for histopathology, then involving the owner to arrive at the best combination of surgical, radiation and/or chemotherapeutic treatment protocols to best suit the patient's quality of life and comfort level of the client.

If your initial histopathology results are inconsistent with your clinical findings, make a request to the diagnostic lab to look at more cuts of the submitted tissue. Don't be afraid to ask for a second opinion from either another pathologist on staff at the lab or from another lab.

Options are increasing for our patients that can give them longer survival times with a better quality of life. They deserve the right to know what treatment options are available and it is our duty as veterinary medical professionals to find them.

Anatomic abnormalities

Variation in number of teeth

Oligodontia – decreased number of teeth. This is usually confirmed with a dental radiograph to see if an adult tooth is present but not erupted. It is seen more often in dogs than in cats. Oligodontia is considered a genetic imperfection and patients that are used for breeding cannot be bred.

Supernumerary – increased number of teeth. The presence of supernumerary teeth can sometimes cause crowding and malalignment of adjacent teeth. The crowding can predispose the patient to periodontal disease. In these cases, dental radiographs should be taken to evaluate the root structure. Extraction is the best treatment option. Supernumerary teeth sometimes do not cause crowding. In these cases, treatment is not required.

Supernumerary Roots – increased number of roots. This condition is clinically significant in cases when the tooth needs to be extracted. A dental radiograph will determine how the tooth should be properly sectioned.

Persistent primary teeth (retained deciduous teeth)

Retained primary teeth can be seen in both cats and dogs. The most commonly seen retained tooth is the canine. Retained primary teeth should be extracted as soon as the adult tooth erupts in order to avoid the permanent teeth erupting out of their normal position. In order to determine which tooth is the primary tooth, a dental radiograph is indicated. Often the primary tooth will be smaller than the permanent tooth with a developed root. The root of the permanent tooth will also have a wide pulp canal, thin dentinal walls, and an open root apex.

Base narrow mandibular canines

This condition occurs due to many factors – brachygnathic mandible, excessive anisognathism or persistent primary teeth. The mandibular canines traumatically occlude with the hard palate. This is a genetically linked condition; hence breeding dogs with this condition should cease being used.

Treatment is by orthodontic means. It can range from encouraging the patient to chew on a ball to installation to performing a gingivoplasty, to the placement of an orthodontic appliance to move the teeth into the proper position.

Gemination

Due to the failure of the tooth bud to split, part of the tooth duplicates. Gemination is usually manifested by two crowns sharing one root. Gemination is only clinically significant when extraction is necessary. A dental radiograph will determine how the tooth should be sectioned properly.

Enameloma or enamel pearl

This condition is a developmental anomaly where a small nodule of enamel forms at the furcation at the cementoenamel junction. In some patients this can be seen bilaterally and cause the tooth to have endodontic problems. When this condition is found on one tooth, it is recommended to radiograph both sides.

Pathology secondary to trauma or disease

Oronasal fistula

An oronasal fistula is an abnormal opening between the oral and nasal cavities. They can occur due to trauma or secondary to periodontal disease. Clinically, the patient may present with a history of sneezing and mucopurulent or hemorrhagic nasal discharge. Confirmation of the oronasal fistula is made using a periodontal probe. The periodontal probe will slide into the nasal cavity and blood maybe seen dripping from the corresponding nostril. Teeth associated with the fistula should be extracted and the lesion should be carefully debrided, flushed, and closed with a mucoperiosteal flap using a long acting absorbable suture.

Facial swelling and draining tracts secondary to periodontal or endodontic disease

When the tooth is affected by periodontal disease or endodontic disease due to trauma, facial swelling and/or draining tracts can be present. Dental radiographs and periodontal probing can rule out whether the cause was endodontic or periodontal disease. The origin of draining tracts can also be located by inserting a gutta percha point into the tract and taking a dental radiograph. For facial swelling secondary to periodontal disease, extraction is the treatment of choice. For facial swelling secondary to endodontic disease, root canal therapy or extraction are the treatment options.

Odontoclastic resorptive lesions

These lesions are seen most commonly in cats, but can be found in dogs as well. They are characterized by a clinically and radiographically evident defect in the enamel, dentin and/or cementum. These defects occur from a stimulation of the odontoclasts which cause the tooth to resorb into the surrounding bone. The treatment of choice for these lesions is extraction. The type of extraction that needs to be done is determined by taking a dental radiograph to see the extent of the disease process.

Fractured teeth

The most commonly fractured tooth in the feline is the canine tooth. The most commonly fractured tooth in the dog is the canine and upper fourth premolar tooth. It is important that these teeth are examined for pulpal exposure using a dental explorer. The pulp of the tooth contains the nerves and the blood vessels and hence is the bacterial "superhighway" of the tooth. Once the pulp is exposed, the disease process may progress in this manner:

Pulpal exposure → Bacterial pulpitis → Pulp necrosis → Apical granuloma → Periapical abscess → Acute alveolar periodontitis → Osteomyelitis → Sepsis

Dental radiographs are important to determine the stage of the disease process. Radiographic findings may include: periapical lysis, apical lysis, asymmetrical endodontic/pulp canals when compared to the contralateral teeth, and secondary destruction of periodontal structures.

The treatment of choice for fractured teeth is extraction or endodontic therapy (vital pulpotomy, root canal therapy). If root canal therapy is provided to the carnassial teeth (upper fourth premolar, lower first molar) or the canine tooth, placing a crown over the treated tooth should be recommended as the nonvital teeth are more brittle.

Tooth subluxations, luxations and avulsions

Tooth subluxation occurs when the periodontium has been damaged so that the tooth is loosened. Treatment for subluxation is soft food and no chew toys for a week.

Luxations are the partial or complete displacement of a tooth from their alveoli due to trauma. Luxated teeth can be extrusive - moved bucally or palatally or intrusive - moved apically. A luxated tooth needs to be repositioned and stabilized using ligature wire and dental acrylics as soon as possible once root fracture has been ruled out.

Teeth that have been avulsed have been completely extruded from the alveolus. Teeth that have been avulsed can be reimplanted within 30 minutes of the trauma by keeping the tooth in saliva or milk. Teeth that have been avulsed due to periodontal disease should not be reimplanted. Reimplanted teeth are held in place using wire and dental acrylic for 6 weeks. Endodontic therapy is recommended 2 weeks after reimplantation.7

Dental attrition and dental abrasion

Dental attrition is the gradual loss of tooth structure that occurs with normal chewing. Pathologic attrition occurs when malocclusion is present causing abnormal tooth to tooth contact. Dental abrasion occurs from chewing on a foreign object (rocks, cage bars, tennis balls, skin allergies). The pulp then responds by laying down tertiary or reparative dentin to protect itself. The tertiary/reparative dentin appears as a dark brown spot on the tooth, which when probed with a dental explorer, feels smooth and cannot be entered. Pulp exposure can occur, so it is recommended to examine all areas of reparative dentin.

Tooth discoloration

Teeth become discolored due to an outside trauma. Fracture of the crown or root may or may not be evident. The discoloration occurs due to lysis of the red blood cells. The hemoglobin breaks down into pigments which then penetrate the dentinal tubules. Discoloration may be transient if the intrapulpal hemorrhage is minor. Dental radiographs are important to determine if endodontic disease is present. The treatment for these teeth is endodontic or exodontic therapy.

Enamel hypoplasia

Enamel hypoplasia occurs due to a disruption of the ameloblasts while the teeth are still developing causing the enamel to be brittle. This disruption can occur due to periods of high fever, Infection (distemper), nutritional deficiencies, and systemic disorders. When the adult teeth erupt, the enamel peels off exposing the underlying dentin. This commonly affects more than one tooth. Composite restoration materials or crowns can be applied to give the mouth a more aesthetically pleasing appearance.

Dental caries

Dental caries are a demineralization of the tooth. As the condition progresses, the tooth structure deteriorates. Caries appear as a dark spot usually on those teeth that have a flat occlusal surface (molars). Clinically, when these teeth are examined with a dental explorer, the lesion will have a soft sticky feel. Dental radiographs are indicated to rule out endodontic involvement and treatment is extraction or restoration.

Lymphocytic plasmacytic stomatitis

This disease is most commonly seen in cats. Patients will present with a history of halitosis, ptyalism, dysphagia, inappetence, and weight loss. The oral examination will show proliferative ulcerative mucosa with a raspberry red, cobblestone appearance. The lesions will be commonly seen around the dentition, but can extend to the palatoglossal folds and fauces. The etiology is unknown, but thought to be autoimmune in nature. A combination of antibiotics, anti-inflammatories and immunomodulators are recommended ± extraction of the teeth in the affected areas. A biopsy of the affected area is indicated to confirm diagnosis.

References

1. Harvey CE, Emily PP: Oral neoplasms, in Small Animal Dentistry. St Louis, Mosby, 1993, pp 297-309.

2. Dhaliwal RS, Kitchell BE, Manfra SM. (1998) Oral tumors in dogs and cats. Part I diagnosis and clinical signs. The Compendium on Continuing Education for the Practicing Veterinarian. 1998, 20 (9): 1011-2022.

3. Lobprise HB, Wiggs RB: Oral examination and recognition of pathology, in The Veterinarian's Companion for Common Dental Procedures. Lakewood, AAHA Press, 2000, pp 29-30.

4. Tholen MA, Hoyt RF: Oral pathology, in Concepts in Veterinary Dentistry. Edwardsville, Veterinary Medicine Publishing, 1982, pp 42-66.

5. Norris AM, Withrow SJ, Dubielzig RR: Oropharyngeal neoplasms, in Veterinary Dentistry. Philadelphia, WB Saunders, 1985, pp 123-138.

6. Caiafa A. Epulides/odontogenic tumors in companion animals. 17th Annual Veterinary Dental Forum, San Diego, CA. November 2003, pp 238-242.

7. Gorrel C. Emergencies, in Veterinary Dentistry for the General Practitioner. Edinburgh, Elsevier, 2004, pp 131-156.