ETIOLOGY/PATHOPHYSIOLOGY
- Rapid and progressive local invasion by cords of neoplastic squamous epithelium arising from the tonsillar fossa into tonsillar lymphoid tissue
- More common in dogs than cats: comprises 9% of canine oral tumors
- Highly locally invasive into soft tissues
- Early metastasis; considered systemic at diagnosis as 70–90% eventually metastasize regardless of local control (lymph nodes, lungs, other distant organs)
- Commonly unilateral; may be bilateral
SIGNALMENT/HISTORY
- Middle-aged or old (range: 2.5–17 years) dogs and cats
- No known breed or sex predilection
- Exact cause unknown; however, 10 times more common in animals living in an urban environment than in those living in a rural environment
- Excessive salivation
- Halitosis
- Dysphagia
- Bloody oral discharge
- Weight loss
CLINICAL FEATURES
- Abnormally large tonsil (oral mass)
- Cervical lymphadenomegaly possible
- Pain upon opening jaw
DIFFERENTIAL DIAGNOSIS
- Lymphoma (generally associated with lymphadenomegaly and bilateral disease)
- Abscess
- Salivary gland tumor
- Metastatic neoplasm (oral melanoma, sarcoma)
- Tonsillitis
- Tonsillar crypt foreign body
- Salivary gland tumor
- Mast cell tumor
DIAGNOSTICS
- Thorough physical examination of the cervical region: detect abnormally large, regional lymph nodes (e.g., mandibular and retropharyngeal)
- Cytological evaluation of lesion
- Fine-needle aspiration samples often nondiagnostic
- Obtain impression smear obtained from an incisional biopsy specimen (wedge); ulceration, inflammation, and secondary infection may limit diagnostic utility
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- Fine-needle aspiration samples often nondiagnostic
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