Encapsulated follicular carcinoma of the thyroid: diagnosis, treatment, and results.

Nineteen cases of encapsulated follicular carcinoma of the thyroid treated at the Massachusetts General Hospital from 1962 to 1979 are reviewed. In all patients the encapsulated nodules had histologic evidence of capsular or vascular invasion. There were 13 women and six men with ages ranging from 14 to 74 years. Eight of the 19 patients underwent large-needle thyroid biopsies before surgery, and in each patient a hypercellular lesion was identified requiring surgery to exclude malignancy. The operative approach was ipsilateral lobectomy with removal of sufficient thyroid tissue to assure that resection margins were free of disease. The size of the tumors ranged from 2 to 6.5 cm in greatest diameter. The mean follow-up was 112 months. Three patients developed ipsilateral neck recurrences. Four patients developed metastases to the bone, brain, or lung. The time from initial operation to recurrence or metastasis ranged from 0 to 241 months (mean, 69 months). There was a 5-year survival rate of 88% and a 10-year survival rate of 78%. Only two of the six patients with complete follow-up died of thyroid malignancy. Of the 16 patients with recurrent or metastatic disease, two died of the disease. No patient whose lesion was 3 cm or smaller developed metastases or recurrences, and of the 10 patients with lesions 3.5 cm or larger, six developed metastatic or recurrent disease. Age was also a prognostic factor, since four of the six patients over 60 years old developed recurrent or metastatic disease.