Risk factors in follicular thyroid carcinomas. A retrospective follow-up study covering a 14-year period with emphasis on morphological findings.

One hundred sixty-seven patients with follicular carcinomas and 88 with atypical adenomas of the thyroid have been followed up for up to 14 years. The influence of tumor invasiveness; tumor extent at time of presentation, including degree of metastatic spread; and age of patients have been evaluated by determining the rate at which distant metastases or deaths occurred during the later course of disease after surgery had been performed. The degree of tumor invasiveness has been found to be of great prognostic weight. Atypical adenomas did not show recurrences during the time of observation. The most important diagnostic distinction made with regard to prognosis was found to be between minimally invasive (encapsulated) and extensively invasive carcinomas.