Reply to Letter to the Editor regarding association of vascular invasion with increased mortality in patients with minimally invasive follicular thyroid carcinoma but not widely invasive follicular thyroid carcinoma

To the Editor: Rajan et al asked proper questions to understand the results of our study regarding management of patients with follicular thyroid carcinoma (FTC). Regarding their first question for the study population, it remains unclear whether H€urthle cell carcinoma (HCC) has a more aggressive behavior than FTC. As Rajan et al cited, a recent population-level analysis by Goffredo et al demonstrated that HCC had more aggressive clinical course than other types of differentiated thyroid cancers, including papillary thyroid carcinoma (PTC) as well as FTC. Whereas, a study by Haigh and Urbach found no major differences in clinicopathologic features and outcome between patients with only FTC and HCC. On the other hand, FTC and HCC is far less prevalent than PTC in iodine-replete areas like Korea. A recent study for comparison of characteristics between patients with FTC and HCC in Korea demonstrated that HCC was thought to follow a similar clinical course as FTC. Thus, 17 patients with a diagnosis of HCC were included in this study. For their second question, we did not perform neck dissection routinely. When any suspicious cervical lymph node was detected by preoperative thyroid ultrasound or by surgeons during operation or preoperative status that might be high-risk grade, we performed central or lateral neck dissection. Thus, lymph node dissection was performed in 21% of the patients, but only 5% of the study population was confirmed with cervical lymph node metastasis in histological specimens. Finally, we agree with guideline recommendations that completion thyroidectomy is necessary when the widely invasive FTC is made after lobectomy, and radioiodine ablation in lieu of completion thyroidectomy is not recommended. A total of 5 patients with widely invasive FTC with vascular invasion underwent lobectomy at the time of analyses. Among these patients, 1 patient had undergone another lobectomy at a local hospital before coming to our hospital, and the patient received radioiodine therapy after surgery. One patient underwent lobectomy and isthmectomy because of thyroid hemiagenesis, and the patient also received radioiodine therapy after an operation. After the time of analyses, 2 patients underwent completion thyroidectomy within 3 months of initial lobectomy, and they were scheduled to receive radioiodine therapy after completion thyroidectomy. One patient underwent lobectomy only because the patient rejected completion thyroidectomy. We hope that this additional information helps you in understanding and reading our article. Thank you.