You are answering a USMLE-style medical question. Question: A 48-year-old female presents with an enlargement of her anterior neck which made swallowing very difficult for 2 weeks now. She has had constipation for the past 6 weeks and overall fatigue. She also had heavy menstrual bleeding; and often feels extremely cold at home. On the other hand, she has well-controlled asthma and spring allergies. On examination, the thyroid is stony hard, tender and asymmetrically enlarged. There is also pain associated with swallowing. Laboratory studies show a serum T4 level of 4.4 μg/dL and a TSH level of 6.3 mU/L. A radionuclide thyroid scanning indicates that the nodule has low radioactive iodine uptake. Which of the following is the most likely pathology to be found in this patient? Options: A) Anaplastic carcinoma B) Medullary carcinoma C) Reidel thyroiditis D) Silent thyroiditis Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.