Clinical and pathologic properties of small differentiated carcinomas of the thyroid gland.

Ninety-one small differentiated thyroid carcinomas less than 10 mm in size treated during the last 33 years were subjected to clinical study. In 44 of the 91 cases, tumor was found incidentally at surgery, while in the remaining 47 a thyroid mass was palpable before operation. A preoperative diagnosis of carcinoma could not be made in nodules less than 5 mm in size. Ultrasonographic examination is now extending the limits of exact diagnosis. Metastasis was found in 16 of 33 patients who had lymph nodes dissected. Metastatic lymph nodes were distributed in the same sites as those with thyroid carcinomas larger than 10 mm. Pathologic examination was carried out in 108 small carcinomas including cases from an affiliated hospital. Histologically, all of them were papillary or follicular carcinomas. The growth pattern of the tumors was divided into 5 groups: 23 were nonencapsulated sclerosing type, 29 encapsulated type without capsule invasion, 48 encapsulated type with capsule invasion, 4 the infiltrative type, and 4 the round type. Lymph node metastasis and intraglandular dissemination were found most frequently in the infiltrative type, followed by the encapsulated type with invasion. The results suggest the necessity of lymph node dissection and lobectomy for patients with these histological types of small carcinomas who had only local removal of the tumor.