Predictive Factors for Ipsilateral or Contralateral Central Lymph Node Metastasis in Unilateral Papillary Thyroid Carcinoma

Objectives: To investigate the incidence and the risk factors for occult ipsilateral or contralateral central neck lymph node (LN)metastasis in patients with unilateral papillary thyroid carcinoma (PTC) and a clinically negative neck.

Summary Background Data: Elective central lymph node dissection (CLND) in patients with PTC remains controversial. There have been few prospective studies assessing accurate histopathologic information and predictive factors for the presence of metastasis to the ipsilateral or contralateral central compartment of the neck in patients with PTC and clinically negative neck nodes.

Methods: We reviewed a prospective protocol of 111 unilateral PTC patients with clinically node-negative necks who have received total thyroidectomy and elective bilateral CLND from 2005 to 2007. The relationships between LN metastasis to the ipsilateral or contralateral central neck compartment and clinico-pathologic factors such as age, sex, size of primary tumor, perithyroidal invasion, lymphovascular invasion, and capsular invasion were analyzed.

Results: Occult central neck LN metastasis was present in 54.1% (60/111). Of these patients, bilateral central LN metastases were present in 50% (30/60), unilateral ipsilateral central LN metastasis in 43.3% (26/60), and unilateral contralateral central LN metastasis in 6.7% (4/60). In the univariate analysis, the rate of ipsilateral central LN metastasis was significantly higher in male patients, high risk MACIS score, carcinoma with a maximal diameter of greater than 1 cm, and carcinoma with lymphovascular invasion (P < 0.05). The rate of contralateral central LN metastasis was significantly higher in cases of carcinoma with a maximal diameter of greater than 1 cm, lymphovascular invasion or histologically proven metastasis to the ipsilateral central LN (P < 0.05). Multivariate analysis showed that the tumor size was an independent risk factor for the presence of ipsilateral central LN metastasis, and the presence of ipsilateral central LN metastasis was the only independent predictor for the presence of contralateral central LN metastasis.

Conclusions: Unilateral PTC with a maximal diameter of greater than 1 cm is associated with a high rate of ipsilateral central neck LN metastasis. Moreover, ipsilateral central LN metastasis is a potential independent predictor of synchronous contralateral central LN metastasis. These findings suggest that contralateral as well as ipsilateral elective CLND, performed during the initial thyroid operation, may be effective in the management of patients with unilateral PTC having a maximal diameter of greater than 1 cm and ipsilateral central LN metastasis.