Thyroid microcarcinoma: a clinical analysis of 262 cases
Objective: To investigate the clinical characteristics, diagnosis and surgical procedure for thyroid microcarcinoma (TMC). Methods: The clinical data of 262 TMC patients confirmed by surgical and pathological findings from January 2011 to June 2014 were reviewed, and were comparatively analyzed with the data of 90 patients with benign thyroid nodules (BTN) undergoing surgery during the same period. Results: Of the 262 TMC patients, 260 cases had papillary carcinoma, 1 case had follicular carcinoma, and 1 case had undifferentiated carcinoma; 246 cases (93.9%) were diagnosed as TMC by intraoperative frozen section; 126 cases (48.09%) were combined with nodular goiter, 18 cases (6.87%) with thyroid adenoma, 27 cases (10.30%) with chronic lymphocytic thyroiditis, and 3 cases (1.15%) with hyperthyroidism. The proportions of low echo, micro calcification, abundant blood flow signal, high TI-RADS grade shown by ultrasound examination in TMC patients were significantly higher than those in BTN patients (all P<0.05), and the sensitivity, specificity, positive predictive value and negative predictive value of high resolution ultrasound for diagnosis of TMC was 83.88%, 80.50%, 91.73% and 65.97% respectively. All TMC patients received surgical treatment that included ipsilateral thyroidectomy plus isthmectomy in 73 cases, subtotal thyroidectomy in 153 cases and total thyroidectomy in 36 cases. One hundred and seventy-two patients underwent lymph node dissection that included central lymph node dissection in 162 cases, and metastasis was found in 45 cases (27.78%) and was found in all the 10 cases who accepted additional functional neck dissection. The central cervical lymph node metastasis in TMC patients was significantly associated with tumor size and number of lesions (χ2=6.77 and 13.11, both P<0.05); the incidence of postoperative complications showed no statistical difference between patients with and without central lymph node dissection (χ2=0.09, P>0.05); no statistical difference was noted in postoperative recurrence rate among patients undergoing different surgical procedures (χ2=2.89, P>0.05). Conclusion: Papillary carcinoma is the main type of TMC and high-resolution ultrasonography is an important diagnostic method for TMC. In TMC patients, proper procedure of ipsilateral thyroidectomy plus isthmectomy or total/subtotal thyroidectomy should be selected according to tumor number and size, and routine ipsilateral central lymph node dissection should be performed, while additional functional neck dissection should be performed in those with highly suspicious or confirmed lateral cervical lymph node metastases.