Clinicopathologic Findings of Micropapillary Carcinomas, according to Tumor Size

Purpose: Papillary thyroid microcarcinomas (PTMC), which are not palpable and have no clinical symptoms are 1.0 cm or less in diameter. The optimal extent of thyroid tumor resection has been controversial. We investigated clinicopathological findings of PTMC of 5 mm or less in diameter for reasonable therapeutic approach. Methods: From, Jan. 2002 to Dec. 2006, 366 patients underwent thyroidectomy for thyroid papillary carcinoma at our institution. Among these patients, 62 patients with a mass measuring less than 5 mm and 103 patients with a mass 5 mm to 1.0 cm were selected. We retrospectively reviewed their medical records. Results: There was no significant difference on the clinical characteristics except multifocality. We performed more unilateral lobectomy, near total thyroidectomy with or without neck node dissection in patients with PTMC of less than 5 mm (P=0.13). In permanent biopsy, lymph node metastasis more frequently occurred in patients with PTMC of less than 5 mm (P=0.03). There were no differences in capsular invasion, distant metastasis or recurrence. Conclusion: In papillary thyroid microcarcinoma less than 0.5 cm, it is very uncommon for capsular invasion, distant metastasis and locoregional metastasis to exist. The extent of tumor resection may be limited less than near total thyroidectomy for suitable cases, because there was no locoregional metastasis or distant metastasis in the follow-up period. Longer follow-up periods would be required to confirm that limited surgery is sufficient for tumors less than 0.5 cm in size.