Encapsulated well-differentiated follicular-patterned thyroid carcinomas do not play a significant role in the fatality rates from thyroid carcinoma.

A cohort of 1039 consecutive cases of thyroid carcinoma treated at a single institution and followed for an average of 11.9 years or until death included 102 encapsulated well-differentiated follicular-patterned tumors that had been diagnosed as carcinoma because of complete capsular invasion and/or papillary carcinoma-type nuclei. None of these cases were among the 67 patients from the cohort who died as a result of their thyroid carcinoma. The results of this study and a critical review of the pertinent literature indicate that tumors with these features are associated with an extremely favorable outcome and that they do not play a significant role in the fatality rate of thyroid carcinoma.