This document discusses the ultrasound characteristics of various thyroid cancers and lesions. It notes that papillary carcinoma is the most common thyroid cancer, often appearing as a solid, hypoechoic nodule with punctate microcalcifications and intranodular vascularity. Anaplastic carcinoma grows rapidly with areas of necrosis. Medullary carcinoma contains echogenic foci related to amyloid and calcification. Follicular lesions cannot be distinguished as benign or malignant without biopsy. Metastases to the thyroid typically appear as a well-defined hypoechoic mass, most often in the lower pole.