Papillary Thyroid Microcarcinoma: Clinicopathologic Characteristics and Treatment Strategy

Abstract

Purpose: The clinical importance of papillary microcarcinoma (PTMC) is debatable. Because PTMC is being diagnosed with increasing frequency, it is important to describe the clinical and histological characteristics that confer aggressive behavior to this cancer. This study was carried out to evaluate the clinical and histological characteristics of PTMC and to determine an appropriate treatment strategy for such cases. Methods: From Jan. 2000 to Dec. 2005, 1,255 patients with small papillary carcinoma, which measured less than 2.0 cm in its greater dimension, underwent total thyroidectomy at our institution. Among these patients, 633 (50.4%) had a thyorid carcinoma less than or equal to 1 cm in diameter (Group A). The clinicopathologic features and treatment outcome of these patients were evaluated and compared with the remaining 622 cases (49.6%) (Group B). Results: For the patients with PTMC (Group A), there were 70 men and 563 women with a median age of 44 years (range; 12∼86). During a mean follow-up of 32.5?18.2 months, 6 patients (0.9%) developed locoregional recurrences and 3 patients (0.5%) showed distant metastases. There was no disease-related mortality in both groups. The disease of group B was more likely to show extracapsular invasion (P＜0.001), invasion to adjacent structures (P＜0.001), and lateral neck node metastasis (P＜0.001) than that of group A. However, there were no significant differences in multifocality (P=0.189), bilaterality (P=0.203), the locoregional recurrence rate (P=0.065) and the distant metastasis rate (P=0.325) between the two groups. On multivariate analysis, locoregional recurrent disease was associated with central lymph node metastases (P=0.033) and lateral neck node metastases (P=0.022). Conclusion: Despite PTMC having less aggressive clinicopathologic parameters as compared with clinical cancer (＞1 cm), some PTMCs show aggressive clinical behavior and locoregional recurrence. The treatment of PTMC should be individualized based on its tumor risk profiles and the clinical presentations. Moreover, performing close follow-up is essential, especially for those patients who present with cervicolateral lymph node metastases.