Multifocality and Total Tumor Diameter Predict Central Neck Lymph Node Metastases in Papillary Thyroid Microcarcinoma

To identify the subgroup of high-risk papillary thyroid microcarcinoma (PTMC) inclined to lymph node metastasis (LNM). Patients who underwent total thyroidectomy with central neck dissection and had a pathologic diagnosis of PTMC between 2003 and 2010 at Wuhan Union Hospital were identified. The frequency of LNM was retrospectively analyzed according to the clinicopathological features. For multifocal lesions, total tumor diameter (TTD) was calculated as the sum of the maximal diameter of each lesion. Last, a meta-analysis was performed with respect to multifocality and LNM in the PTMCs. The proportion of LNM was similar between multifocal PTMCs with TTD a parts per thousand currency sign 1 cm and unifocal tumors with diameter a parts per thousand currency sign 1 cm (37.5 vs. 30 %, P = 0.463). LNM frequency was also similar between multifocal PTMCs with 1 < TTD a parts per thousand currency sign 2 cm (TTD greater than 1 cm but less than or equal to 2 cm) and unifocal tumors with 1 < diameter a parts per thousand currency sign 2 cm (56.8 vs. 64.9 %, P = 0.330). However, LNM frequency was significantly higher in multifocal PTMCs with TTD > 1 cm than unifocal tumors with diameter a parts per thousand currency sign 1 cm (60.4 vs. 30 %, P < 0.001). A meta-analysis of nine publications plus our own data with a total 1,586 PTMCs demonstrated that multifocality was significantly associated with LNM risk (odds ratio 1.9, 95 % confidence interval 1.5-2.4). Multifocal PTMC with TTD > 1 cm has a similar risk of LNM as a clinical papillary cancer. Routine central neck dissection is recommended in this subgroup of patients.