The clinical impact of microscopically positive tumor margin in papillary thyroid cancer is not well studied. The aim of this study is to evaluate the clinical importance of a microscopically positive margin for recurrence in papillary thyroid cancer patients and to examine whether recurrence and recurrence-free survival were affected by the location of the positive margin—anterior or posterior.

Methods

We conducted a retrospective cohort study at a single institution. From January 1997 to June 2015,6,293 papillary thyroid cancer patients who underwent total thyroidectomy with or without neck dissection (central and/or lateral) at the Thyroid Cancer Center of Samsung Medical Center (Seoul, South Korea) were included in the analyses.

Results

Of the 6,293 papillary thyroid cancer patients, an operative margin was microscopically involved in 313 (5.0%) on final pathologic report. The mean follow-up time was 77.5 months, and locoregional recurrence was observed in 244 (3.9%) patients. The presence of a microscopically positive margin did not increase the risk of locoregional recurrence (adjusted hazard ratio = 1.079, P = .140) after adjustment for other statistically significant factors in the Cox proportional hazard model. In addition, posterior positive margin was not a risk factor for locoregional recurrence as well (adjusted hazard ratio = 1.24, P = .672). In a propensity score–matching analysis, a microscopically positive margin did not increase the risk of locoregional recurrence.

Conclusion

Microscopic involvement of the operative margin in papillary thyroid cancer patients, whether anteriorly or posteriorly, does not appear be an independent prognostic factor in recurrence-free survival rates.