Papillary and Follicular Thyroid Cancer: A Selective Approach to Diagnosis and Treatment

Thyroid carcinoma comprises a group of widely differing tumors ranging from slow-growing, well-differentiated neoplasms that ordinarily have an excellent prognosis to anaplastic cancers that usually have a dismal out­ come. This review is concerned with differentiated thyroid cancers-papil­ lary and follicular-the most common types encountered clinically and about which the most controversy exists regarding management. Benign thyroid nodules are very common, whereas clinically detectable thyroid cancer is relatively rare. Accordingly, a selective approach to the management of thyroid nodules is necessary to avoid SUbjecting an unac­ ceptably large number of persons to surgery. When a nodule is found to be papillary or follicular thyroid cancer, opinions differ regarding optimal therapy. Indeed, lively debate continues, not only around the extent of surgery required, but also about the indica­ tions for therapeutic 1311 and the efficacy of thyroid hormone in controlling tumor growth. This is in part a consequence of the wide range of'biologic behavior displayed by these tumors, which makes the task of evaluating therapy difficult (1-3). Papillary and follicular thyroid cancers are often indolent neoplasms with a benign course, including many associated with prior head and neck irradiation (4). Even with distant metastases, patients may live for decades (5, 6). On other occasions death from differentiated thyroid cancer may occur within a few years of diagnosis. An understanding of the clinical behavior and prognosis of these tumors can lead to both an