37-year-old female with contrast CT of the neck for evaluation of possible adenopathy.
Answer: Tonsillar hypertrophy
Tonsillar hypertrophy or hyperplasia is a sequela of chronic or recurrent tonsillitis and may be an incidental imaging finding, as in this case. The imaging characteristics of tonsillar hypertrophy include enlargement of bilateral adenoidal, palatine, or lingual tonsils with absence of intra-tonsillar fluid collections or adjacent inflammatory stranding on non-contrast CT. Hypertrophied tonsils enhance less than in tonsillar inflammation on contrast CT. In addition, prominent tonsillar crypts with trapped air (Figure 1) or tonsilloliths secondary to prior infection or inflammation may be present. The former, which is well delineated in this case, should not be confused with tonsillar abscess.
Differential diagnoses for tonsillar enlargement include, but are not limited to, tonsillar hypertrophy, tonsillitis, tonsillar abscess, tonsillar retention cyst, tonsillar squamous cell carcinoma, and tonsillar non-Hodgkin’s lymphoma. Tonsillitis typically presents as bilateral tonsillar enlargement with hyperenhancement and tonsillar striations on contrast CT. Tonsillar abscess presents as often unilateral, enlarged tonsil (greater than 2 cm in size) with central low attenuation and peripheral rim enhancement as well as possible effacement of ipsilateral oral airway due to its space-occupying nature on contrast CT. Both of these entities are often associated with adjacent inflammatory stranding and/or reactive cervical adenopathy. Tonsillar retention cyst is likely a sequela of prior tonsillitis and is incidentally found on the imaging studies as discrete, focal tonsillar fluid without surrounding enhancement or edema. Lastly, malignancy involving the tonsils results in tonsillar enlargement. The imaging characteristics of tonsillar squamous cell carcinoma include unilateral, mildly enhancing, poorly circumscribed tonsillar mass associated with mucosal ulcer and malignant cervical adenopathy, commonly in ipsilateral Level II. Tonsillar non-Hodgkin’s lymphoma is another differential consideration and typically presents as unilateral, well circumscribed or invasive tonsillar mass associated with often large, non-necrotic cervical adenopathy.