Papillary Thyroid Microcarcinomas: Experience at a Single Institute

Han, In Woong; Choe, Jun Ho; Han, Wonshik; Noh, Dong Young; Oh, Seung Keun; Youn, Yeo Kyu

Abstract

PURPOSE
Papillary thyroid microcarcinomas (PTMCs) have the same histological features as papillary thyroid cancer, but they are 1.0 cm or less in diameter. They can metastasize to the regional lymph nodes and distant sites, but its ability to cause significant morbidity and mortality has been questioned. Because of this reason, the extent of thyroid tumor resection remains an issue of controversy. This study is aimed at identifying the statistically significant factors that are associated with recurrence and we also wanted to devise an appropriate surgical treatment plan for PTMC patients.
METHODS
The retrospective review (350 cases, 1990.1~2004. 11) was obtained from Seoul National University Hospital (SNUH). The mean age at the time of diagnosis was 46.5± 11.0 (yrs) (range: 12~75). The mean overall length of follow- up was 37.70± 36.03 months (range: 1~169). The PTMCs were treated with total and subtotal thyroidectomy or lobectomy. The invasiveness and lymph node metastasis (LNM) from 350 PTMCs were analyzed according to the size, multiplicity, bilaterality of the tumor and the perithyroidal invasion. Fishers exact test and the exact logistic regression test were used for the stratified analysis.
RESULTS
350 of the 2187 papillary carcinoma were PTMCs. There were 296 females (84.6%) and 54 males (15.4%) in the study. Invasion into the perithyroidal tissue was common (128/336, 38.1%). There were 68 patients with LNM among the 312 total patients (21.7%). The group with either perithyroidal invasion or LNM showed a significantly higher recurrence rate than those group having neither one (4.8% vs. 10.9%, 4.5% vs. 19.1%, respectively). Even for tumor smaller than 1 cm, a larger-sized tumor resulted in a poorer prognosis.
CONCLUSION
PTMC is an early stage carcinoma with the capability of tissue invasion, lymph node metastasis and multiplicity. Based on this study, total thyroidectomy is recommended for significant portion of the PTMCs. Furthermore, more careful imaging studies (such as neck ultrasonography or neck CT scan) are needed to detect contralateral lesions or neck lymph node metastasis.