Thyroid carcinoma is an uncommon malignan­ ing the available non-human lines, as models cy. In the vast majority of patients, if treated for cell cycle studies and oncogene/anti­ appropriately, it is associated with a benign oncogene regulation, because they are unaware clinical course. Why then does it hold a con­ of the often fundamental dichotomy between tinuing fascination for so many physicians? thyroid malignancy and prognosis. Third, the The answer is probably directly dependent very nature of the benign clinical course has suggested to the major health research fund­ on the very benign nature of most thyroid ing agencies that thyroid cancer is not worthy maligllancies. While there are terrible excep­ of study in a time of scarce resources. tions, the follicular and papillary thyroid can­ Nothing could be further from the truth. cers behave in a way quite alien to "common" This gratifying clinical course is the very reason neoplasia, since they grow and metastasize why the study of human thyroid cancer has the slowly. We believe that if only we could under­ potential for contributing further to our fun­ stand such a transformed state, we would be able to learn a great deal about the normal and damental understanding of malignancy and, abnormal regulation of the cell cycle and im­ perhaps more importantly, the mechanisms by prove our understanding of cancer. which the human body can resist neoplastic However, recent advances in the biology of cells.