Disorders of the Oral Cavity

A 7-year-old dog presents with a rapidly growing mass on the gingiva. What are the top 3 differentials?

• Malignant Oral Neoplasm: Malignant Melanoma or Squamous Cell Carcinoma (SCC).

• Acanthomatous Ameloblastoma (Acanthomatous Epulis): A benign but locally aggressive epulis characterized by rapid growth, local invasion, and underlying bone lysis.

• Abscess or Inflammatory Granuloma: Tooth root abscess, trauma-induced granuloma, or Peripheral Giant Cell Granuloma.

What are the most common oral and pharyngeal malignant neoplasms in dogs versus cats?

• Dogs: Squamous Cell Carcinoma (SCC) and Malignant Melanoma.

• Cats: Squamous Cell Carcinoma (SCC) and Fibrosarcoma.

• (Note: Transmissible Venereal Tumor [TVT] also affects the oral/pharyngeal cavity).

What non-neoplastic or non-malignant conditions should be included in the differential diagnosis list for an oral mass?

• Abscess ( secondary to trauma, foreign body, or tooth root infection)

• Hematoma

• Sialocele

• Sialadenitis or other salivary gland disorders

• Myiasis

List benign oral tumors found in small animals.

• Papilloma

• Epulides (Peripheral Odontogenic Fibroma, Canine Acanthomatous Ameloblastoma, Peripheral Giant Cell Granuloma)

• Fibroma

• Lipoma

• Chondroma

• Osteoma

• Hemangioma

• Hemangiopericytoma

• Histiocytoma

What is the Etiology and Signalment of Canine Oral Papillomas?

• Etiology: Caused by Canine Papillomavirus; contagious and transmitted dog-to-dog.

• Signalment: Usually affects young dogs.

Explain the lesion appearance and treatment for canine oral papillomas

• Lesion Appearance: Starts as pale, smooth elevations, progressing into rough, closely packed fronds ("cauliflower-like") within 3–4 weeks.

• Course & Treatment: Usually self-limiting, resolving spontaneously within 4–8 weeks. Severe or obstructive cases require surgical excision.

How are epulides (gingival masses near incisors) classified histologically?

• Class I: Peripheral Odontogenic Fibroma

• Class II: Acanthomatous Ameloblastoma

• Class III: Peripheral Giant Cell Granuloma

How is peripheral odontogenic fibroma clinically presented?

Pedunculate, non-ulcerated, slow-growing, and non-invasive mass. Most common in dogs >5 years old.

State the histological and anatomical findings of peripheral odontogenic fibroma.

• Attached to alveolar bone

• Contains bone or cemento-osseous matrix and odontogenic epithelium

• Hypercellularity correlates with ulceration and inflammation.

• Does not involve the periodontal ligament space

• Etiology Note: May represent reactive fibromatous hyperplasia of the gingival ligament rather than a true neoplasm.

Detail the clinical behavior, predisposing breeds, and features of Canine Acanthomatous Ameloblastoma.

• Clinical Behavior: Benign histologically, but exhibits rapid growth, aggressive local tissue invasion, and underlying bone lysis. Does not metastasize.

• Signalment: Median age of 7–10 years. Breed predispositions include Shetland Sheepdogs and Old English Sheepdogs.

• Primary Cell Component: Basal cells.

What are the key features of Peripheral Giant Cell Granuloma?

• Clinical Features: Rapid growth with prominent inflammatory and ulcerative mucosal changes. Higher recurrence rate reported in cats.

• Histology: Multinucleated giant cells as the main cellular component, accompanied by osteoid and woven bone formation.

Outline the 7-step systematic diagnostic workup for an oral mass.

1. Examine: Visual inspection of the oral cavity and mass.

2. Palpate: Palpate mass and assess regional lymph nodes (Mandibular, Parotid, Medial Retropharyngeal).

3. Imaging: Dental radiographs, head/skull radiographs, or CT to evaluate bony invasion.

4. Obtain Tissue: Fine Needle Aspirate (FNA) or biopsy (incisional/excisional).

5. Histopathology: Definitive microscopic diagnosis.

6. Stage: (If malignant) Abdominal ultrasound, 3-view thoracic radiographs, and lymph node aspirates.

7. Treatment Plan: Formulate surgical, radiation, or medical plan.

Which regional lymph nodes drain the oral cavity, and which ones are normally palpable?

• Regional Nodes: Mandibular, Parotid, and Medial Retropharyngeal lymph nodes.

• Palpability: Only the mandibular lymph node is normally palpable in health; the parotid and medial retropharyngeal nodes are generally not palpable unless enlarged.

Describe the surgical resection margins and treatment protocols for non-aggressive epulides versus acanthomatous ameloblastoma.

• Non-Aggressive Lesions (e.g., Peripheral Odontogenic Fibroma): Surgical resection using conservative margins accompanied by extraction of the associated tooth.

• Acanthomatous Ameloblastoma: Maxillectomy or mandibulectomy with 1cm clean surgical margins due to local bone invasion.

• Adjunctive Therapy: Radiation therapy for non-resectable, incompletely excised, or recurrent tumors.

• Monitoring: Recheck schedule at 2 weeks, 6 months, 12 months, and annually thereafter following complete excision.

What is the overall prognosis for epulides following appropriate surgical management?

• Peripheral Odontogenic Fibroma: Excellent prognosis following complete surgical resection.

• Acanthomatous Ameloblastoma: Excellent prognosis following complete surgical resection with wide margins. Smaller size and rostral anatomic location are positive prognostic indicators (detected earlier and easier to excise).

What is a sialocele, how does it present, and how is it definitively diagnosed and treated?

• Etiology: Accumulation of saliva within subcutaneous tissues surrounding a damaged salivary gland or duct, most commonly secondary to trauma (or idiopathic).

• Presentation: Large, fluid-filled, painless cervical swelling under the jaw, tongue (ranula), or pharynx.

  • Oral Cavity Location: Causes dysphagia.

  • Pharyngeal Location: Causes gagging and dyspnea.

• Diagnosis:

  • FNA: Yields honey-like, viscous, clear-to-bloody fluid containing low numbers of non-degenerate neutrophils and vacuolated macrophages.

  • Imaging: Contrast sialogram or CT scan to identify the affected salivary gland unit.

• Treatment: Surgical drainage of the fluid collection paired with surgical excision of the affected salivary gland/duct complex.

Describe the clinical signs and treatment plan for Sialadenitis.

• Definition: Primary or secondary inflammation of a salivary gland.

• Clinical Presentation: Painful swelling along the vertical ear canal, caudal to the mandible, or in the orbital/retrobulbar area (causing exophthalmos).

  • Associated with systemic signs including fever, lymphadenopathy, severe pain on opening the mouth, and pain on direct palpation. Dysphagia occurs secondary to pain or physical obstruction.

• Treatment: Gland drainage, aggressive pain management, and appropriate antimicrobial (antibiotic) therapy.

Describe the pathophysiology, signalment, and breed predispositions for Masticatory Muscle Myositis (MMM).

• Pathophysiology: Autoimmune disorder characterized by autoantibodies directed specifically against Type 2M muscle fibers unique to the muscles of mastication (temporalis, masseter, pterygoid).

• Signalment: Large-breed, young-adult to middle-aged dogs.

• Breed Predispositions:

  • Highly overrepresented in German Shepherds.

  • Severe, destructive myofiber inflammation seen in Rottweilers, Samoyeds, and Doberman Pinschers.

  • Reported in Cavalier King Charles Spaniel littermates with clinical onset before 12 weeks of age.

Contrast the acute versus chronic clinical presentations of Masticatory Muscle Myositis.

• Acute Stage: Bilaterally swollen, painful temporalis and masseter muscles, pyrexia, and hesitation or inability to chew.

• Chronic Stage: Marked, severe bilateral atrophy of the temporalis and masseter muscles, jaw trismus (inability to open the mouth/jaw stiffness), and deep enophthalmos.

How is MMM diagnosed and treated?

• Diagnosis:

  • Presumptive: History and clinical presentation (inability to open jaw, masticatory muscle atrophy).

  • Supportive/Serology: Detection of circulating antibodies to Type 2M fibers (highly specific).

  • Definitive Confirmation: Muscle biopsy of the temporalis or masseter muscles.

• Treatment:

  • Immunosuppressive therapy: Prednisolone @ $2.2\text{ mg/kg/day}$ combined with Azathioprine ($50\text{ mg/m}^2$). Once clinical control is achieved, medications are slowly tapered to the lowest effective dose.

  • Nutritional Support: Placement of a gastrostomy tube (G-tube) until the patient can open their mouth and ingest food independently.

• Prognosis: Good if treated early in the acute stage, though long-term or lifelong continuous immunosuppressive therapy may be required.