Autonomously functioning (hot) nodule of the thyroid gland. A clinical and histopathologic study of 17 cases

The authors present the clinical and pathologic findings of 17 patients with autonomously functioning (hot) nodule of the thyroid (AFNT). The patients were 13 to 68 years of age, and 12 were female. Five had obvious laboratory findings of hyperthyroidism, but the other 12 were euthyroid. Fifteen patients had solitary or multiple benign nodules. The remaining two had autonomously functioning carcinomas; one of these patients had a papillary carcinoma with no distant metastases, and the other had a follicular carcinoma with widespread metastases. Total thyroidectomy was performed in one patient, subtotal thyroidectomy was performed in four, and hemithyroidectomy in eight. Diagnostic large needle biopsy was performed in only four patients. Of the 13 patients undergoing thyroidectomy, 3 had multiple hot nodules, and 10 had a solitary hot nodule. The size of the nodules ranged from very small to 6 cm, with no definite correlation found between the size of the nodule and thyroid function. Pathologically, cystic change and hemorrhage to various degrees were common features of AFNT. On histologic examination of the nodules, 13 were diagnosed as follicular adenoma (6 predominantly macrofollicular; 4 mixed micro-, normo-, and macrofollicular; and 3 predominantly papillary) and 2 as adenomatous goiter (1 predominantly papillary and 1 predominantly macrofollicular). The remaining two were diagnosed as carcinoma (1 follicular variant of papillary carcinoma and 1 follicular carcinoma). Two children had benign nodules showing a predominantly papillary architecture. Microcarcinoma outside the nodules was found in two patients, and both microcarcinomas were a papillary type. The AFNTs showed characteristic pathologic findings, and the pathologic differentiation of AFNTs from usually observed nonfunctioning (cold) nodules was not difficult. Pathologists should pay particular attention to AFNTs showing a papillary architecture, because these papillary lesions are sometimes mistaken for papillary thyroid carcinoma.