Papillary thyroid microcarcinomas located at the middle part of the middle third of the thyroid gland correlates with the presence of neck metastasis.

Background: Papillary thyroid microcarcinomas (PTMCs), located at upper poles of the thyroid, are associated with lateral neck metastasis (LNM) according to previous reports. Controversy remains regarding the correlation between the location of PTMCs and central neck metastasis (CNM).

Methods: Medical records of 949 patients with PTMCs diagnosed between 2010 and 2013 were reviewed retrospectively. With a subdivision of the middle third of the thyroid gland, correlations between tumor location and CNM/LNM along with other clinicopathologic factors were analyzed by binary logistic regression.

Results: PTMCs located in the middle part of the middle third of the thyroid gland (MPMT) showed the greatest rate of CNM (57.5%) among all locations. PTMCs located at isthmus showed the second greatest rate of CNM (44.3%). In the multivariate analysis, MPMT, tumor size >0.5 cm, young and middle age, male sex, multifocality within the affected lobe, and capsular invasion were correlated with CNM. PTMCs located at upper poles and MPMT showed comparatively high rates of LNM (8.6% and 8.3%). Consistent with previous reports, an upper pole location, MPMT, and a tumor size >0.5 cm greatly correlated with LNM in the multivariate analysis. Eleven patients had skip metastases, which only occurred with upper/lower pole locations and MPMT.

Conclusion: PTMCs located in the MPMT correlated with both CNM and LNM. Tumor location along with other clinicopathologic factors such as young and middle age, male sex, and tumor size >0.5 cm could facilitate preoperative stratification and guide operative management for patients with PTMC.