Background: Medullary thyroid carcinoma (MTC) has a poorer prognosis than differentiated thyroid cancers; however, comprehensive data on the long-term outcomes of MTC remain scarce. This study investigated the extended clinical outcomes of MTC and aimed to identify prognostic factors. Methods: Patients diagnosed with MTC between 1980 and 2020 were retrospectively reviewed. Their clinical characteristics, longterm clinical outcomes, and prognostic factors for recurrence and mortality were analyzed. Results: The study included 226 patients (144 women, 82 men). The disease-specific survival (DSS) rates for all MTC patients at 5-, 10-, 20-, and 30-year intervals were 92.7%, 89.4%, 74.3%, and 68.1%, respectively. The recurrence-free survival (RFS) rates were 71.1%, 56.1%, 40.2%, and 32.1% at these intervals. DSS was comparable between the groups from 1980–2009 and 2010–2020 (P=0.995); however, the 1980–2009 group had significantly lower RFS rates (P=0.031). The 2010–2020 group exhibited greater extents of surgical and lymph node dissection (P=0.003) and smaller tumors (P=0.003). Multivariate analysis identified extrathyroidal extension as the strongest prognostic factor for both RFS and DSS. Age >55 years and tumor size of ≥2 cm were also significant prognostic factors for DSS, while hereditary disease and lymph node metastasis were significant for RFS. Survival analysis after propensity-score matching of rearranged during transfection (RET)-negative and non-screened RET-positive groups showed comparable DSS but longer RFS in the RET-negative group. Conclusion Extrathyroidal extension was identified as the strongest prognostic factor for RFS and DSS. Older age and larger tumor size were associated with decreased DSS, while RET mutation and lymph node metastasis significantly impacted RFS.

Background: Medullary thyroid carcinoma (MTC) has a poorer prognosis than differentiated thyroid cancers; however, comprehensive data on the long-term outcomes of MTC remain scarce. This study investigated the extended clinical outcomes of MTC and aimed to identify prognostic factors. Methods: Patients diagnosed with MTC between 1980 and 2020 were retrospectively reviewed. Their clinical characteristics, longterm clinical outcomes, and prognostic factors for recurrence and mortality were analyzed. Results: The study included 226 patients (144 women, 82 men). The disease-specific survival (DSS) rates for all MTC patients at 5-, 10-, 20-, and 30-year intervals were 92.7%, 89.4%, 74.3%, and 68.1%, respectively. The recurrence-free survival (RFS) rates were 71.1%, 56.1%, 40.2%, and 32.1% at these intervals. DSS was comparable between the groups from 1980–2009 and 2010–2020 (P=0.995); however, the 1980–2009 group had significantly lower RFS rates (P=0.031). The 2010–2020 group exhibited greater extents of surgical and lymph node dissection (P=0.003) and smaller tumors (P=0.003). Multivariate analysis identified extrathyroidal extension as the strongest prognostic factor for both RFS and DSS. Age >55 years and tumor size of ≥2 cm were also significant prognostic factors for DSS, while hereditary disease and lymph node metastasis were significant for RFS. Survival analysis after propensity-score matching of rearranged during transfection (RET)-negative and non-screened RET-positive groups showed comparable DSS but longer RFS in the RET-negative group. Conclusion Extrathyroidal extension was identified as the strongest prognostic factor for RFS and DSS. Older age and larger tumor size were associated with decreased DSS, while RET mutation and lymph node metastasis significantly impacted RFS.

Background: Medullary thyroid carcinoma (MTC) has a poorer prognosis than differentiated thyroid cancers; however, comprehensive data on the long-term outcomes of MTC remain scarce. This study investigated the extended clinical outcomes of MTC and aimed to identify prognostic factors. Methods: Patients diagnosed with MTC between 1980 and 2020 were retrospectively reviewed. Their clinical characteristics, longterm clinical outcomes, and prognostic factors for recurrence and mortality were analyzed. Results: The study included 226 patients (144 women, 82 men). The disease-specific survival (DSS) rates for all MTC patients at 5-, 10-, 20-, and 30-year intervals were 92.7%, 89.4%, 74.3%, and 68.1%, respectively. The recurrence-free survival (RFS) rates were 71.1%, 56.1%, 40.2%, and 32.1% at these intervals. DSS was comparable between the groups from 1980–2009 and 2010–2020 (P=0.995); however, the 1980–2009 group had significantly lower RFS rates (P=0.031). The 2010–2020 group exhibited greater extents of surgical and lymph node dissection (P=0.003) and smaller tumors (P=0.003). Multivariate analysis identified extrathyroidal extension as the strongest prognostic factor for both RFS and DSS. Age >55 years and tumor size of ≥2 cm were also significant prognostic factors for DSS, while hereditary disease and lymph node metastasis were significant for RFS. Survival analysis after propensity-score matching of rearranged during transfection (RET)-negative and non-screened RET-positive groups showed comparable DSS but longer RFS in the RET-negative group. Conclusion Extrathyroidal extension was identified as the strongest prognostic factor for RFS and DSS. Older age and larger tumor size were associated with decreased DSS, while RET mutation and lymph node metastasis significantly impacted RFS.

Background: Medullary thyroid carcinoma (MTC) has a poorer prognosis than differentiated thyroid cancers; however, comprehensive data on the long-term outcomes of MTC remain scarce. This study investigated the extended clinical outcomes of MTC and aimed to identify prognostic factors. Methods: Patients diagnosed with MTC between 1980 and 2020 were retrospectively reviewed. Their clinical characteristics, longterm clinical outcomes, and prognostic factors for recurrence and mortality were analyzed. Results: The study included 226 patients (144 women, 82 men). The disease-specific survival (DSS) rates for all MTC patients at 5-, 10-, 20-, and 30-year intervals were 92.7%, 89.4%, 74.3%, and 68.1%, respectively. The recurrence-free survival (RFS) rates were 71.1%, 56.1%, 40.2%, and 32.1% at these intervals. DSS was comparable between the groups from 1980–2009 and 2010–2020 (P=0.995); however, the 1980–2009 group had significantly lower RFS rates (P=0.031). The 2010–2020 group exhibited greater extents of surgical and lymph node dissection (P=0.003) and smaller tumors (P=0.003). Multivariate analysis identified extrathyroidal extension as the strongest prognostic factor for both RFS and DSS. Age >55 years and tumor size of ≥2 cm were also significant prognostic factors for DSS, while hereditary disease and lymph node metastasis were significant for RFS. Survival analysis after propensity-score matching of rearranged during transfection (RET)-negative and non-screened RET-positive groups showed comparable DSS but longer RFS in the RET-negative group. Conclusion Extrathyroidal extension was identified as the strongest prognostic factor for RFS and DSS. Older age and larger tumor size were associated with decreased DSS, while RET mutation and lymph node metastasis significantly impacted RFS.

The indolent nature and favorable outcomes associated with papillary thyroid microcarcinoma have prompted numerous prospective studies on active surveillance (AS) and its adoption as an alternative to immediate surgery in managing low-risk thyroid cancer. This article reviews the current status of AS, as outlined in various international practice guidelines. AS is typically recommended for tumors that measure 1 cm or less in diameter and do not exhibit aggressive subtypes on cytology, extrathyroidal extension, lymph node metastasis, or distant metastasis. To determine the most appropriate candidates for AS, factors such as tumor size, location, multiplicity, and ultrasound findings are considered, along with patient characteristics like medical condition, age, and family history. Moreover, shared decision-making, which includes patient-reported outcomes such as quality of life and cost-effectiveness, is essential. During AS, patients undergo regular ultrasound examinations to monitor for signs of disease progression, including tumor growth, extrathyroidal extension, or lymph node metastasis. In conclusion, while AS is a feasible and reliable approach for managing lowrisk thyroid cancer, it requires careful patient selection, effective communication for shared decision-making, standardized follow-up protocols, and a clear definition of disease progression.

The American Joint Committee on Cancer/Union for International Cancer Control (AJCC/UICC) staging classification of thyroid cancer can predict death but cannot determine the type and frequency of follow-up testing. Risk stratification is a concept proposed by the American Thyroid Association that uses additional prognostic factors that are not included in the AJCC/UICC classification, such as number or size of metastatic lymph nodes, genetic mutations, and vascular invasion in follicular cancer, to further refine the prognosis of thyroid cancer. The risk of recurrence was categorized as low, intermediate, and high risk, and the need for total thyroidectomy, radioiodine therapy, or thyroid-stimulating hormone suppression was determined depending on each risk level. This approach has been accepted worldwide, and the previous recommendations of the Korean Thyroid Association followed a similar line of thinking but these have been modified in the revised 2024 guidelines.For the revised initial risk stratification, after careful review of the results of the recent meta-analyses and large observational studies and after a multidisciplinary meeting, four major changes were made: 1) thyroid cancer was reclassified according to the World Health Organization (WHO) 2022 tumor classification system; 2) recurrence risk was stratified by combining encapsulated follicular variant papillary thyroid cancer, follicular thyroid cancer, and oncocytic thyroid cancer, which have similar recurrence risk and associated factors, into follicular-patterned tumor; 3) low-risk groups were defined as those with a known recurrence rate of ≤5%, high-risk groups were upgraded to those with a known recurrence rate of ≥30%, and intermediate-risk groups were those with a recurrence risk of 5–30%; and 4) the intermediate risk group had the recurrence rate presented according to various clinicopathological factors, mainly based on reports from Korea. Thus, it is recommended to evaluate the initial risk group by predicting the recurrence rate by combining each clinical factor in individual patients, rather than applying the recurrence rate caused by single risk factor.

Only a small percentage of patients (2-5%) with differentiated thyroid cancer (DTC) exhibit distant metastasis at the initial diagnosis or during the disease course. The most common metastatic sites of DTC are the lungs, followed by the bones. Radioactive iodine (RAI) therapy is considered the primary treatment for RAI-avid distant metastatic DTC. Depending on the characteristics of metastatic lesions, local treatment such as surgical resection, radiofrequency ablation, and external beam radiation therapy may be considered for some patients with metastatic DTC. Slowly growing and asymptomatic metastases can be monitored with follow-up while receiving thyroid-stimulating hormone (TSH) suppression therapy. In patients with a limited number of lung metastases and good performance status, surgical removal of the metastatic lesions may be considered. Systemic therapy should be considered for patients with progressive RAI refractory DTC. In this clinical guideline, we aim to outline the treatment principles for patients with lung, bone, and brain metastases of DTC.

Differentiated thyroid cancer demonstrates a wide range of clinical presentations, from very indolent cases to those with an aggressive prognosis. Therefore, diagnosing and treating each cancer appropriately based on its risk status is important. The Korean Thyroid Association (KTA) has provided and amended the clinical guidelines for thyroid cancer management since 2007. The main changes in this revised 2024 guideline include 1) individualization of surgical extent according to pathological tests and clinical findings, 2) application of active surveillance in low-risk papillary thyroid microcarcinoma, 3) indications for minimally invasive surgery, 4) adoption of World Health Organization pathological diagnostic criteria and definition of terminology in Korean, 5) update on literature evidence of recurrence risk for initial risk stratification, 6) addition of the role of molecular testing, 7) addition of definition of initial risk stratification and targeting thyroid stimulating hormone (TSH) concentrations according to ongoing risk stratification (ORS), 8) addition of treatment of perioperative hypoparathyroidism, 9) update on systemic chemotherapy, and 10) addition of treatment for pediatric patients with thyroid cancer.

Background: Thyroid cancer screening has contributed to the skyrocketing prevalence of thyroid cancer. However, the true benefit of thyroid cancer screening is not fully understood. This study aimed to evaluate the impact of screening on the clinical outcomes of thyroid cancer by comparing incidental thyroid cancer (ITC) with non-incidental thyroid cancer (NITC) through a meta-analysis. Methods: PubMed and Embase were searched from inception to September 2022. We estimated and compared the prevalence of high-risk features (aggressive histology of thyroid cancer, extrathyroidal extension, metastasis to regional lymph nodes or distant organs, and advanced tumor-node-metastasis [TNM] stage), thyroid cancer-specific death, and recurrence in the ITC and NITC groups. We also calculated pooled risks and 95% confidence intervals (CIs) of the outcomes derived from these two groups. Results: From 1,078 studies screened, 14 were included. In comparison to NITC, the ITC group had a lower incidence of aggressive histology (odds ratio [OR], 0.46; 95% CI, 0.31 to 0.7), smaller tumors (mean difference, −7.9 mm; 95% CI, −10.2 to −5.6), lymph node metastasis (OR, 0.64; 95% CI, 0.48 to 0.86), and distant metastasis (OR, 0.42; 95% CI, 0.23 to 0.77). The risks of recurrence and thyroid cancer-specific mortality were also lower in the ITC group (OR, 0.42; 95% CI, 0.25 to 0.71 and OR, 0.46; 95% CI, 0.28 to 0.74) than in the NITC group. Conclusion Our findings provide important evidence of a survival benefit from the early detection of thyroid cancer compared to symptomatic thyroid cancer.

Thyroid hormone plays an important role in the process of implantation of a fertilized egg in the endometrium, as well as in the division and development of the fertilized egg. In addition, maternal thyroid hormone is essential for the formation and development of the fetal brain, nervous system, and bones. Therefore, when maternal thyroid hormone is insufficient, complications such as miscarriage, stillbirth, low birth weight and preeclampsia increase. Guidelines for the diagnosis and treatment of thyroid dysfunction during pregnancy were established and published by the American Endocrine Society, the American Thyroid Association, and the European Thyroid Society. The Korean Thyroid Society also published recommendations for diagnosis and treatment of thyroid disease during pregnancy and postpartum in 2014. However, since the revised guidelines of the American Thyroid Association were published in 2017, many studies, including large-scale randomized controlled trials, have been published in relation to thyroid and pregnancy, and the need to revise the existing recommendations has emerged in Korea.The main revisions of this recommendation are changes in the normal range of TSH during pregnancy, detailed description of treatment policies according to pregnant women’s autoantibodies and thyroid function status. Also, a description of the effect of thyroid autoantibodies on assisted reproductive procedures has been added.