Review Question - QID 213508

A 52-year-old woman presents to the emergency department with 1-week of anxiety and palpitations. She says that she has also had increasing difficulty swallowing food over the last 3 months but thought that might be because she recently changed her diet. She also admits to getting headaches and having the sensation of feeling "hot" more than before. On physical exam, she is found to have 3 nodules in the front of her neck that move when she swallows. A biopsy is taken of a nodule and a representative histological slide is shown in Figure A. Which of the following best describes the most likely cause of this patient's symptoms?