Abstract
Objective: This retrospective study aimed to analyze the ultrasound (US) imaging features of solitary papillary thyroid carcinoma (PTC) located in the isthmus and to assess the risk factors for lymph node metastasis (LNM) and tumor capsular invasion.Methods: We included a total of 135 patients with solitary PTC located in the isthmus. All the cases underwent US, total thyroidectomy, and prophylactic central lymph node dissection. Patients' demographic and thyroid isthmus nodules' US characteristics, as well as risk factors associated with LNM and tumor capsular invasion, were analyzed.Results: It was revealed that the occurrence of LNM was higher in male patients than in female patients (P < 0.001). As risk factors, the size of PTC in the isthmus was found to be associated with LNM and tumor capsular invasion (P = 0.005 and 0.000, respectively). The area under the receiver operating characteristic curve (AUC) of the size of the isthmus PTC was 0.64 [95% confidence interval (CI) = 0.55–0.72], indicating a probability for LNM. The AUC value for tumor capsular invasion was 0.77 (95% CI: 0.68–0.83). When the threshold was set to 1.1 cm, the larger size indicated that there was a probability of occurrence of LNM with sensitivity and specificity of 47.4 and 73.7%, respectively. When the threshold was set to 0.7 cm, the larger size indicated that there was potentially a tumor capsular invasion, with sensitivity and specificity of 80.6 and 56.3%, respectively. Wider-than-tall nodules were found to be significantly different from those in LNM and tumor capsular invasion (P = 0.038 and 0.030, respectively). There were significant differences in tumor capsular invasion in extrathyroidal extension (ETE) compared with smooth or ill-defined and lobulated or irregular nodules (P = 0.017).Conclusions: This study showed that the incidence of LNM in male patients was higher than that in female ones. When a US image shows a thyroid isthmus nodule with a wider-than-tall shape, LNM and tumor capsular invasion were likely to occur. When a US image shows a thyroid isthmus nodule with an ETE, tumor capsular invasion was likely to occur. ETE and wider-than-tall may be indicators of FNA under US guidance, even though the size of thyroid isthmus nodule may be <1 cm.
Highlights
The most frequent endocrine malignancy is thyroid cancer, and the most common histological subtype of thyroid cancer is papillary thyroid cancer (PTC), accounting for about 80% of all cases with thyroid cancer
The present study aimed to investigate the relationship between tumor capsular invasion and lymph node metastasis (LNM) associated with PTC in the isthmus
The area under the ROC curve (AUC) values for the size of thyroid nodule with LNM and tumor capsular invasion in the isthmus were 0.64 and 0.77, respectively
Summary
The most frequent endocrine malignancy is thyroid cancer, and the most common histological subtype of thyroid cancer is papillary thyroid cancer (PTC), accounting for about 80% of all cases with thyroid cancer. PTC often occurs in patients 20– 55 years old, especially in women [1,2,3,4]. The 10-year survival rate of PTC is high, it can reach about 93%, whereas some special locations of PTC have shown certain invasive behavior, and about 30–90% of PTCs may have clinical or occult cervical lymph node metastasis (LNM) [5]. A number of scholars have studied PTC location in the isthmus; because the isthmus is located directly in front of the trachea, it covers the second to fourth tracheal rings, and it is covered by the strap muscles, fascia, and skin in the middle of the neck [8]. Studies have shown that PTC is located in the isthmus with a higher rate of LNM, tumor capsular invasion, and extrathyroidal extension (ETE) [9,10,11]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
