ABSTRACT
Anaplastic thyroid cancer (ATC) is rare and one of the most aggressive thyroid cancers. It is almost uniformly lethal. ATC is an undifferentiated cancer of follicular cells of thyroid that have lost all their functions like iodine uptake, thyroglobulin synthesis and thyroid-stimulating hormone dependence. The cancer is characterized by aggressive local disease with high rates of distant metastases most commonly lung and early lethal clinical outcome. ATC can arise de novo or from dedifferentiation of preexisting differentiated thyroid cancer (DTC) of follicular cell origin. In 20–50% of patient, there is history of long-standing goiter that has started rapid enlargement and genetic studies show shared genetic alterations with DTC like BRAF and RAS. The treatment is difficult and includes surgery, accelerated hyperfractionated external beam radiation therapy, chemotherapy in a localized disease and palliation in wide spread disease. During the last 50 years, the clinical courses of the disease have not changed; however, there is now more understanding of the genetics and clinicopathology, which has risen a hope of newer treatment options.
