Biological behavior and prognosis of encapsulated papillary carcinoma of the thyroid: experience of a Japanese hospital for thyroid care.

Abstract

A subtype of papillary thyroid carcinoma that is totally surrounded by a fibrous capsule is designated an encapsulated carcinoma. In this study, we investigated the biologic behavior and prognosis of this type of carcinoma. The clinicopathologic parameters and prognosis were compared between 1207 patients with conventional papillary carcinoma and 149 patients diagnosed as having encapsulated papillary carcinoma who underwent initial surgery between 1987 and 1996. Sex, age, and the tumor size of the encapsulated carcinoma did not differ from those of patients with conventional papillary carcinoma. However, none of the patients with encapsulated carcinoma showed distant metastasis at diagnosis. The incidences of pathologic lymph node metastasis and clinically apparent lateral node metastasis in patients with encapsulated carcinomas were significantly lower than in those with a conventional papillary carcinoma. Ten patients (6.7%) with encapsulated carcinoma showed recurrence after surgery. After excluding recurrence to the remnant thyroid, disease-free survival of patients with encapsulated carcinoma was significantly better than that of those with conventional papillary carcinoma. None of the patients with encapsulated carcinoma died of carcinoma. Encapsulated papillary carcinoma exhibits a more indolent biologic behavior than conventional papillary carcinoma. However, because recurrence to locoregional and even distant organs can be seen, careful and constant postoperative follow-up is recommended.