Review Question - QID 210777

An 19-year-old woman presents to her primary care physician because she has been feeling increasingly lethargic over the last 6 months. Specifically, she says that she feels tired easily and has been cold even though she is wearing lots of layers. Her medical history is significant for seasonal allergies but is otherwise unremarkable. When prompted, she also says that she has a hard time swallowing food though she has no difficulty drinking liquids. Physical exam reveals a midline mass in her neck. Which of the following structures would most likely be seen if this patient's mass was biopsied?