Prognosis in carcinoma of the thyroid varies more widely and consistently with the histologic pattern than perhaps any other neoplasm. This fact has been observed particularly in relation to the papillary forms, which have a good although not necessarily an excellent prognosis. The follicular form is associated with only a fair prognosis, and the anaplastic forms are invariably rapidly fatal.
A major proportion of the differentiated carcinomas of the thyroid exhibit a mixed pattern of both papillary and follicular elements. The clinical implications of the respective roles of these two components in the mixed forms have not been emphasized by most studies of thyroid cancer. The usual classifications do not recognize the mixed forms as such, assigning given tumors to either papillary or follicular categories according to predominant cell type. In an effort to evaluate the clinical significance of predominance of either the papillary or follicular elements in the mixed