Question: A 37-year-old man presents with a single, firm mass within the thyroid gland. This patient's father developed a tumor of the thyroid gland when he was 32 years of age. Histologic examination of the mass in this 37- year-old male reveals organoid nests of tumor cells separated by broad bands of stroma, as seen in the photomicrograph below. The stroma stains positively with Congo red stain and demonstrates yellow-green birefringence. The most likely diagnosis of this lesion is?