Poorly Differentiated and Undifferentiated Thyroid Cancer

Abstract

Thyroid carcinoma in its differentiated form is associated with an excellent long-term prognosis, with surgical resection and the use of radioactive iodine providing effective treatment and cure in a high proportion of patients. In contrast to well-differentiated thyroid cancer (WDTC), poorly differentiated forms of thyroid cancer exist which are associated with a more aggressive clinical course and a correspondingly less favorable prognosis. At the extreme of the spectrum of differentiation of thyroid cancers, undifferentiated (anaplastic) thyroid cancer (UTC) is one of the most biologically aggressive and lethal of human malignancies, displaying rapid invasive growth and early metastatic dissemination. It is recognized that some thyroid cancers display a degree of differentiation and biological behavior which is intermediate between WDTC and UTC in this spectrum, and this group has been referred to as poorly differentiated thyroid cancer (PDTC).