[Lateral neck lymph node metastasis in cN0 papillary thyroid carcinoma]

To study the pattern of lymph node spread in papillary thyroid carcinoma (PTC) with clinically negative node (cN0).

A total of 106 patients with cN0 PTC who underwent total or subtotal thyroidectomy plus unilateral or bilateral lateral neck dissection (LND, level II-V or level I-V) at West China Hospital of Sichuan University between April 2004 and August 2010 were analyzed retrospectively.

The lateral neck lymph node metastasis in cN0 PTC was significantly associated with sex (male, P = 0.007), tumor stage (T3/T4, P = 0.006), tumor size (> 1 cm, P = 0.014) and the number of positive central lymph nodes (≥ 2, P < 0.001), but not with age and multifocal tumor. Level III (47/116, 40.5%) was the most prevalent metastatic site, followed by level IV (41/116, 35.3%), level II (18/116, 15.5%) and level V (2/29, 6.9%). Of the cases with lymph node metastases in level III and IV, 89.8% (79/88) of primary thyroid tumors existed in the lower and middle sites of the thyroid lobes, while in the cases with lymph node metastases in level II, 77.8% (14/18) of primary thyroid tumors in the upper sites of the thyroid lobes, and 83.3% of cases with level II metastases were accompanied with level III metastases. Two cases with level V metastases were accompanied with metastases in levels II, III and IV.

LND should be considered for cN0 PTC in male, with T3/T4 lesions and positive central lymph nodes ≥ 2, and the range of dissection should include level III and IV. Dissection of level II should be considered in cN0 PTC with primary tumor localized in the upper site of the thyroid lobe or with level III metastasis. Dissection of level V should be considered at present of metastases in level II, III, and IV. For cN0 PTC with tumor size < 1 cm, confined to the thyroid and without lymph node metastasis in the central compartment, LND is not recommended.