A 14-year-old teenager undergoing medical screening at public clinic.
On ultrasound of the thyroid gland, plus-tissue was visualized along its lower edge, it resembles a thymus gland in localization, but at this age thymus is usually no longer visualized.
Dif. diagnosis: persistent thymus, lymphoma, etc.
CT recommended.
For those who do not believe that lymphoma may look like this, and are used to making a benign histological diagnosis by ultrasound in 100% of cases, the case of a colleague from the Netherlands - external link
In addition, a small quote from a respected guide:
"The thymus is a prominent normal anterior mediastinal structure in children up to 8 years of age. From age 2 to 8 years, the thymus remains a prominent sonographic landmark when scanning the mediastinum, even though it is less obvious on chest radiographs. Progressive fatty replacement makes the thymus blend with mediastinal fat and become sonographically invisible in older children and adults. Sonograpraphic visualization of the thymus in an adult suggests neoplastic disease."