Encapsulated papillary neoplasms of the thyroid. A study of 14 cases followed for a minimum of 10 years.

Fourteen cases of encapsulated papillary thyroid neoplasm in which extracapsular extension was not observed and a minimum of 10 years follow-up was available are herein presented. The cases were divided into three categories: encapsulated papillary carcinomas (five cases), which had cytologic features typical of papillary thyroid carcinoma (vesicular or indented nuclei) and an entirely or predominantly thick capsule with capsular invasion; encapsulated papillary neoplasms of undetermined malignancy (seven cases), in which the cytologic features were also typical of papillary carcinoma but the capsule was predominantly thin (less than 0.1 mm thick) or was thick without capsular invasion; and follicular adenomas with papillae (two cases), which resembled follicular adenomas cytologically (rounded, stippled nuclei and Hürthle cell change) but contained a significant number of papillary structures (both cases had an entirely or predominantly thin capsule). The only evidence of malignant behavior in the entire series was a cervical lymph node metastasis in one case of encapsulated papillary carcinoma; the "encapsulated papillary neoplasms of undetermined malignancy" were so labeled because other authors have reported "encapsulated papillary carcinomas without capsular invasion" and it was therefore thought that the malignant potential of this category is as yet best considered undefined.