Analysis of Risk Factors of Level V Lymphatic Metastasis for Papillary Thyroid Carcinoma with pN1b

To explore the risk factors of level V lymphatic metastasis in papillary thyroid carcinoma (PTC) patients with pN1b.

Patients were selected if they presented with a suspicious level III or IV lymph node metastasis and underwent surgery by hemi or total thyroidectomy with a lymph node dissection (levels III, IV, VI, and VII). For these patients, if frozen section showed a positive level III or IV node, then levels II and V nodes were resected. Univariate analysis was performed using the chi-square test for some factors, including age, sex, tumor location, multifocal lesions, tumor size, local invasion of primary focus, status of cervical lymphatic metastasis, TNM staging, tumor deposits (independent tumor nodules), and the metastasis to more than 5 central lymph nodes. Then, the factors with statistical significance indicated by the above univariate analysis underwent multivariate analysis.

Univariate analysis indicated that the level V lymphatic metastasis was significantly associated with simultaneous metastases to levels II, III, and IV, simultaneous metastases to levels III and IV, and tumor deposits (all p < 0.05), but it was not significantly associated with age, sex, tumor location, multifocal lesions, tumor size, local invasion of primary focus, other cervical lymphatic metastasis, TNM staging, and the metastases to more than 5 central lymph nodes (all p > 0.05). Multivariate analysis suggested that the simultaneous metastases to levels III and IV and tumor deposits were the risk factors of level V lymphatic metastasis.

The simultaneous metastases to levels III and IV and tumor deposits are independent risk factors of level V lymphatic metastasis. The patients with pN1b PTC who have simultaneous metastases to levels III and IV or/and tumor deposits may have the risk of level V lymph node metastasis.