Objective  The objective of this study was to analyze risk factors for pathologically negative reoperation in patients with differentiated thyroid cancer.

  Methods  The clinical data of patients underwent reoperation for differentiated thyroid cancer from January 2013 to December 2017 in Peking Union Medical College Hospital were assessed retrospectively. Based on postoperative pathology, patients were further divided into pathology positive and negative groups. The demographic characteristics, operation information, pathological findings, and ultrasonography outcomes were compared between the two groups.

  Results  A total of 218 patients were included. Seventy cases were males and 148 cases were females. The male to female ratio was 1:2.11. The average age was 43.7±12.7 years. All patients were diagnosed with local recurrence or metastasis before the reoperation. Twenty-seven patients had negative postoperatively pathological results, while other 191 had positive ones. Compared with the positive group, the patients of the negative group were older (49.3±12.6years vs. 42.9±12.5 years, P=0.013) and had fewer multifocal lesions (7.4% vs. 24.6%, P=0.045). The two groups had no significant difference in gender, operation information, tumor size, and ultrasonography outcomes (all P>0.05).

  Conclusions  Pathologically negative reoperation for differentiated thyroid cancer is not rare. The age and multifocality of the primary surgery may be associated with negative reoperative pathology.