Purpose: Lymph node metastases (LNM) in papillary thyroid microcarcinomas (PTMC) are common. PTMC greater than 5 mm are considered to be more aggressive. Tumor greater than 5 mm is predictive factor for occurrence of LNM in PTMC, although there are insufficient data regarding this fact. The purpose of this study was to explore the relation between LNM and patients with small (≤5mm) and large (>5mm) PTMC. The second target was to determine the frequency of multifocality, bilaterality and capsular invasion in small and large PTMC, and their relation with LNM occurrence. Methods: This study included 257 patients with PTMC. In all patients total thyroidectomy was performed, and lymph node checking of central and lateral neck region using sentinel lymph node (SLN) biopsy in clinically N0 patients, or modified radical neck dissection in clinically N1b patients or in case with positive SLN. Results: LNM were detected in 33% of the patients, 27% in the central neck region and 20% in the lateral neck region with 6.23% of skip metastases. LNM were significantly frequent in large PTMC compared with small (46 vs 24%), in the central region (38 vs 19%) and the lateral region (28 vs 14%), with skip metastases 7.62% and 5.26%, respectively. Bilaterality and capsular invasion were frequent in large PTMC. Multifocality and male gander were predictive factors for LNM in small PTMC, while capsular invasion was the only predictive factor in large PTMC. Conclusions: Although LNM are frequent in large PTMC, the percentage of LNM is not negligible in small PTMC, especially if they are multifocal.

The study was reviewed by the Medical Ethics Committee of the School of Medicine in Belgrade, Republic of Serbia and performed in accordance with the ethical standards laid down in the appropriate version of the 1964 Declaration of Helsinki. Our study was approved by the Institutional Review Board of the Institute of Oncology and Radiology of Serbia and conducted with the understanding and consent of all subjects involved.