When the histological examination indicates differentiated thyroid cancer(DTC), especially with intermediate-risk features, there is no unanimity on the need to proceed with completion thyroidectomy(CT). This study aims to assess the histologic parameters that influenced the decision to perform CT.

This retrospective study included patients with histologic diagnosis of DTC who underwent thyroid lobectomy(TL) between 2019 and 2022. Patients were categorized into two groups: Group1 included those who underwent TL alone, whereas Group2 included patients who underwent CT. Differences in terms of histologic parameters (tumor size, aggressive variants, gross extrathyroidal extension, vascular invasion, presence of >4 neoplastic emboli, perithyroidal lymph node metastasis, multifocality) were analyzed.

Group1 included 314 patients(68.1%), whereas Group2 147 patients(31.9%). Tumor size, aggressive variants, vascular invasion and presence of >4 neoplastic emboli were associated to CT(p<0.001). Multivariate analysis confirmed associations between CT and tumor size(p<0.001), aggressive variant(p=0.018), and vascular invasion(p<0.001). The ROC analysis determined a cutoff of 20 mm for CT. Considering only the last 3 years, multivariate analysis identified association between CT and tumor size and vascular invasion only(p<0.001). In the linear regression analysis, the presence of two or fewer factors was identified as negatively correlate to CT(p=0.002).

This study suggests a trend toward more selective CT indications, with tumor size and vascular invasion being key factors influencing the decision to perform CT. Additionally, the lack of more than two aggressive histologic parameters does not indicate a requirement for CT. Individualized therapeutic approach might be necessary in case of DTC with intermediate-risk histologic features after lobectomy.