ABSTRACT
Anaplastic thyroid carcinoma (ATC) is the dark side of thyroid malignancy. One can only wonder why the thyrocyte, the progenitor of the usually easily controlled well-differentiated thyroid cancers, also gives rise to virulent, relentless, and almost universally lethal anaplastic thyroid cancer (Fig. 1). Although only 2-5% of thyroid carcinomas are anaplastic, they account for approximately 50% of the 1200 annual deaths in the United States from thyroid malignancy (1). In the United States from 1973 to 1991, ATC constituted 1.4% of thyroid cancer with an estimated yearly incidence of 1.6%. This represents an annual incidence of 300 cases (2).
