Abstract
Cribriform-morular thyroid carcinoma is a rare type of thyroid cancer. It has a strong association with familial adenomatous polyposis (FAP), a hereditary genetic disorder that predisposes individuals to the development of numerous polyps in the colon and rectum. We describe the case of a young female patient who presented with an enlarging goiter, notably without detectable thyroid nodules or masses on ultrasound, who after total thyroidectomy was found to have cribriform-morular thyroid carcinoma. This diagnosis led to genetic testing and diagnosis of FAP syndrome. We demonstrate that this rare thyroid carcinoma may present with nonsuspicious findings on sonographic evaluation while being a valuable harbinger in the diagnosis of FAP syndrome.