Don't forget to look at tonsils if you have huge medial retropharyngeal lymph nodes......

Computed tomographic appearance of canine tonsillar neoplasia: 14 cases

Florence Thierry, Maurizio Longo, Evi Pecceu, Davide D. Zani, Tobias Schwarz

Background
The palatine tonsil, a rare site for canine oral neoplasia, is most commonly affected by squamous cell carcinoma (SCC), followed by melanoma and lymphoma. The study aimed to describe the computed tomography (CT) features of canine tonsillar neoplasia and assess whether these features could differentiate between neoplastic and non-neoplastic tonsils. Such differentiation is essential for diagnosis and staging of oropharyngeal tumors in dogs.

Methods
This retrospective descriptive study reviewed the CT scans of 14 dogs diagnosed with tonsillar neoplasia. Diagnostic criteria included tonsillar cytology or histology and contrast-enhanced CT imaging of the head and neck. Key CT features such as tonsillar size, attenuation, enhancement patterns, and regional lymph node characteristics were analyzed. Lymph node enlargement, heterogeneity, and loss of the hypoattenuating hilus were recorded. Statistical comparisons were conducted for neoplastic versus non-neoplastic tonsils.

Results
Neoplasia Types: Carcinoma was the most common diagnosis (11/14 dogs), followed by melanoma (2/14) and lymphoma (1/14). Bilateral neoplasia was noted in 50% of cases.

Tonsillar Findings: Neoplastic tonsils were significantly larger than non-neoplastic ones (median size: 15.8 mm vs. 9.7 mm). However, in 3 cases, neoplastic tonsils showed minimal enlargement.

Lymph Node Characteristics: Marked medial retropharyngeal lymphadenomegaly (≥18 mm width) was present in 67% of cases. Ipsilateral lymphadenopathy was frequently observed (73%), often accompanied by heterogeneity and absence of the hypoattenuating hilus.

Advanced Features: Invasion of the soft palate or surrounding structures occurred in 29% of cases, but distant metastases were rare, with pulmonary involvement documented in only one dog.

Limitations
The small sample size restricted statistical power. Variability in CT protocols and contrast administration limited the analysis of enhancement patterns. Non-standardized imaging timing may have affected attenuation values. Histology confirmation was unavailable for all enlarged lymph nodes, leading to potential underreporting of metastatic involvement.

Conclusions
Although CT features did not definitively differentiate neoplastic from non-neoplastic tonsils, lymph node appearance provided valuable diagnostic clues. Marked medial retropharyngeal lymphadenomegaly with heterogeneity and loss of the hypoattenuating hilus strongly indicated neoplasia. The study highlights the importance of CT in the diagnostic and staging process of canine tonsillar neoplasia, especially in cases with minimal tonsillar enlargement or isolated lymphadenopathy.

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