[Role of level VI lymph nodes metastasis in cervical metastasis of patients with papillary thyroid cancer].

OBJECTIVE: To study the features of level VI lymph node metastasis in papillary thyroid cancer (PTC) and the distribution of metastatic lymph nodes in the neck levels, and to provide evidences for the treatments of cervical metastasis in patients with PTC.

METHODS: Ninety-seven PTC cases were reviewed retrospectively. The tumors in all cases were limited to one side lobe. Of them, 72 patients were cN0 and 25 patients were cN+; 32 patients with tumors ≤ 1 cm and 65 patients with tumors > 1 cm. Pathological examinations of frozen biopsies of level III and IV lymph nodes were taken in the operation. The extent of lymph node dissection depending on pathological examination results of level III and IV lymph nodes and the size and location of the tumor. For the patients with metastatic lymph nodes in level III and IV, the modified neck dissection including level VI was performed. Ipsilateral VI lymph node dissection was performed for the patients with tumors ≤ 1 cm and bilateral VI lymph node dissection for the patients with tumors > 1 cm or with extra-thyroidal invasion.

RESULTS: In 97 patients, 122 sides of VI lymph node dissection were performed. Positive nodes in level VI were found in 45.1% (55/122) patients. The positive rates of nodes metastases in level VI were 45.8% (33/72) for 72 patients with cN0 and 76.0% (19/25) for 25 patients with cN+ respectively, with a significant difference statistically (χ(2) = 6.790, P = 0.009). Positive rates of node metastases in level VI were 65.0% (13/20) in 10 patients with extra-thyroidal invasion and 41.2% (42/102) in 77 patients without extra-thyroidal invasion respectively, with a significant difference statistically (χ(2) = 3.833, P = 0.047). Positive rate of node metastasis in level VI was 43.8% (14/32) in 32 patients with tumors ≤ 1cm. Of 65 patients with tumors > 1cm, ipsilateral and bilateral node metastasis rates were 69.2% (45/65) and 23.1% (15/65) respectively, with a significant difference statistically (χ(2) = 5.843, P = 0.016).

CONCLUSIONS: Cervical lymph node metastasis in level VI can occur at early stage of PTC. The patients with extra-thyroidal invasion were prone to have lymph node metastasis in level VI. Ipsilateral positive nodes in level VI can exist in the patients with tumors ≤ 1 cm, while bilateral positive nodes in level VI can occur in the patients with tumors > 1 cm. The cervical lymph node metastasis of PTC may take place in level VI alone or in level VI and in lateral neck levels simultaneously. Pathological examinations of frozen biopsies of level III and IV lymph nodes should be taken for PTC patients, when the presence of positive lymph node, the modified neck dissection including level VI should be performed.