Level VI node size as a predictor of malignancy in papillary thyroid cancer

To determine the incidence of metastatic lymph nodes < 1 cm in routine level VI neck dissections in papillary thyroid cancer (PTC).

Retrospective chart review.

Tertiary referral hospital.

A retrospective review was conducted of all patients who had thyroid surgery and routine level VI neck dissection for PTC from June 2005 to February 2009. The number of lymph nodes present, node size, and malignancy status were recorded. Patients with level VI micrometastases (positive nodes < 1 cm) were compared with those with no positive nodes.

Forty-six patients had level VI neck dissection for PTC, with a total of 379 lymph nodes. No patient had permanent hypocalcemia or recurrent laryngeal nerve injury. Nodes > or = 1 cm had a 77% likelihood of being positive (95% confidence interval [CI] 0.58-1.00), whereas nodes < 1 cm had a 24% (95% CI 0.20-1.00) likelihood of being positive. Seventeen (37%) patients had micrometastases only. Older age, male sex, and primary tumour > 5 cm were not predictive of an increased risk of micrometastases. Patients with extrathyroidal extension were significantly more likely to have micrometastases (p < .05).

With a significant percentage of metastatic level VI neck nodes < 1 cm in PTC, the decision to perform a level VI neck dissection cannot be based on preoperative ultrasound size criteria alone. Routine level VI neck dissection is a safe addition to thyroid surgery for PTC. We could identify no preoperative risk factors to predict the likelihood of micrometastases.