Occult contralateral central neck metastasis in papillary thyroid carcinoma with preoperatively documented ipsilateral lateral neck metastasis.

Background: This study was conducted to evaluate risk factors and long-term prognosis of contralateral central neck metastasis (CCNM) in papillary thyroid cancer (PTC) patients with ipsilateral lateral neck metastasis. We present clinical evidence to aid in surgical decision-making regarding the extent of central neck dissection (CND), focusing on separation between ipsilateral and contralateral sides.

Methods: A total of 379 PTC patients who underwent total thyroidectomy and concomitant bilateral central neck dissection with ipsilateral lateral neck dissection (LND) at a single institution was retrospectively included between January 1997 and December 2015.

Results: The median follow-up time was 83.2 months, the mean age was 44.3 years, and the mean tumor size was 1.5 cm. Among the study sample, 266 patients were female (70.2%) and 113 (29.8%) were male. Of 379 patients, CCNM was present in 34.6%. In multivariate analysis, male sex (adjusted OR = 2.46, p = 0.002), bilaterality (adjusted OR = 2.58, p = 0.004), number of metastatic ipsilateral central lymph nodes (adjusted OR = 1.15, p = 0.002), number of metastatic lateral lymph nodes (adjusted OR = 1.48, p < 0.001), and three-level metastasis (adjusted OR = 2.46, p = 0.012) were identified as risk factors of CCNM. Overall recurrence occurred in 6.0% and 11.5% of patients in the CCNM (-) group and CCNM (+) group, respectively. In addition, contralateral recurrence was observed in 1.2% patients and 0.8% patients in the CCNM (-) group and CCNM (+) group, respectively. However, CCNM did not significantly increase risk of recurrence (adjusted HR = 1.01, p = 0.981).

Conclusions: Although the probability of pathological CCNM is not negligible, CCNM was not associated with higher risk of recurrence. This study suggest that central neck dissection may be limited to the ipsilateral side, and the result regarding prognosis of CCNM may help to avoid bilateral CND so that it could have potential to minimize unnecessary surgery-related complications such as recurrent laryngeal nerve(RLN) injury or hypoparathyroidism.