Will medullary thyroid cancer always show in a thyroid ultrasound ? if not how do they find it?

Thyroid cancer: Hello. Unfortunately cancer of the thyroid will not show up on an ultrasound. A nodule or a growth in the thyroid can be seen and identified. A tissue or needle biopsy is needed to examine the cells for cancer. An excisional biopsy if needed will provide the pathologist the entire gland which then will be examined and a diagnosis rendered.