A study on thyroid nodules without preoperative malignant features

When a thyroid nodule has malignant features found by some examinations (e.g. Echo, FNAC, CT), we perform surgical resection. But if the thyroid nodule does not have malignant feature, there is still the possibility of malignancy, especially when the nodule is large. In the case of large pre-operatively benign thyroid nodules, we therefore consider a diagnostic lobectomy. There is, however, no definite recommendation how large a nodule should be before a lobectomy is performed, and how many malignancies exist in pre-operatively benign nodules. In our hospital, we consider surgical resection when the diameter of the thyroid nodule is over 3 cm. In this study, we analyze pre-operatively benign thyroid nodules in which surgical resection was performed in our hospital, how many malignant nodules there were and what the characteristics were between benign or malignant nodule. From 2005 April to 2012 June, 351 patients underwent a lobectomy in our hospital, 70 of which were pre-operatively benign thyroid nodules with diameters of over 3 cm. We analyzed the pathological findings and compared the nodule diameters, serum thyroglobulin, FNAC's classification and some characteristics of echography between pathologically benign and malignant cases. Fifty-eight patients (83%) had pathologically benign nodules, and 12 patients (17%) had malignant nodules. In 58 benign nodules, 33 nodules (47%) were adenomatous goiter, 24 patients (34%) had follicular adenomas and 1 nodule (1%) was an atypical adenoma. In the 12 malignant patients, 8 patients (11%) had papillary adenocarcinoma and 4 patients (6%) had follicular adenocarcinoma. Almost no significant characteristics were found concerning malignancy, in diameter, serum thyroglobulin, class of FNAC and features of echography. As for complications after surgery, hypothyroidism occured in 4 patients (6%), and neither hypoparathyroidism nor vocal fold paralysis occurred. We concluded that pre-operatively benign thyroid nodule that were over 3 cm in diameter had about a 17% possibility of malignancy. Examinations may not distinguish whether such pre-operatively benign tumors are benign or malignant before surgical resection. We should therefore consider whether to perform therapeutic surgery or not in such patients.