Correlation between Growth Pattern of MicroPTC without Extrathyroidal Extension and Central Lymph Node Metastasis

Abstract

Objectives:

Although prognostic significance of central lymph node (CLN) metastasis in micropapillary thyroid cancer (microPTC) is controversial, thorough removal of metastatic LN may reduce the recurrence rate. Histological or clinical predicting factors for CLN metastasis have been studied to determine the adequate surgical extent or postoperative adjuvant therapy to eradicate metastatic LN. However, histological features inside primary tumor were not considered as a predicting factor for metastasis. In this study, we evaluated the relationship between specific histological findings of microPTC and CLN metastasis.

Methods:

We reviewed patients who underwent total thyroidectomy and central lymph node (CLN) dissection for microPTC from January to December 2011. Fibrotic change, growth pattern and architecture of tumors were used as histological factors. Histologic findings were classified according to the degree of fibrosis (<10%, 10-50%, >50%) and growth pattern (well-defined/extracapsular spread (ECS)/spiculated or infiltrative). The relationship between CLN metastasis and those histological or clinical factors were analyzed.

Results:

Of 353 patients, 162 had CLN metastasis (45.9%). Chi-square test showed that age, gender, and tumor size were not related to CLN metastasis. Well-defined tumor (n = 28) had lower rate of CLN metastasis (14.3%) than tumor with ECS (46.5%) or infiltrative pattern (32.8%, P = 0.019). Multivariate analysis showed that growth pattern was only risk factor for CLN metastasis (odds ratio = 1.972, P = 0.022).

Conclusions:

Follicular or infiltrative growth pattern of microPTC is an independent risk factor for CLN metastasis. This report suggests that tumor behavior in the primary tumor plays an important role in CLN metastasis.