In patients with differentiated thyroid cancer (DTC), initial recurrence risk stratification based on clinical, histopathological, and perioperative data remains the key determinant for guiding management strategies during the first 1-2 years post-treatment. However, the adoption of ongoing risk stratification (ORS), which dynamically reassesses risk by integrating longitudinal clinical data and treatment response, enables more precise long-term prognostic assessment and facilitates highly individualized management. Building upon recent guidelines, the 2026 KTA guideline has been further refined by incorporating robust evidence from large-scale national cohorts and comprehensive systematic reviews. These updated recommendations outline contemporary concepts of ORS, risk-adapted TSH suppression targets, optimized surveillance modalities for recurrence detection, and disease-specific long-term follow-up strategies. Reflecting the paradigm shift toward de-escalated treatment, this revision integrates evolved perspectives on TSH suppression intensity, the clinical interpretation of thyroglobulin levels, and tailored follow-up intervals. These evidence-based recommendations aim to minimize unnecessary treatment and excessive surveillance in the large proportion of patients with excellent prognosis after initial therapy, while ensuring that each patient receives appropriately tailored and effective long-term management.

Hypersensitivity reactions (HSRs) to iodinated contrast media (ICM) can range from mild cutaneous symptoms to life-threatening anaphylaxis. In patients with a history of ICM hypersensitivity, avoidance of the culprit agent is generally recommended. This case report describes a successful desensitization in a 56-year-old man with recurrent HSRs to multiple agents including ioversol, iohexol, iobitridol, and iopamidol. Intradermal testing was performed to identify potentially safe alternatives; however, all tested agents, including iohexol, ioversol, iobitridol, iopamidol, iodixanol, iomeprol, and iopromide, yielded positive results. Given the clinical necessity of transcatheter arterial chemoembolization, a 13-step rapid desensitization protocol with iodixanol was implemented. The procedure was completed without any breakthrough reactions. This case highlights desensitization as a feasible and effective strategy for patients with hypersensitivity to multiple ICM agents.

Background: Mycoplasma pneumoniae is a major cause of community-acquired pneumonia (CAP) in children, with a rising incidence of macrolide resistance. Early diagnosis is crucial for reducing the disease burden; however, current diagnostic tools have limitations.We evaluated the diagnostic accuracy of serological assays and their performance based on symptom onset in children with CAP. Methods: From September 2023 to September 2024, we prospectively enrolled children with CAP, classified as M. pneumoniae pneumonia (MPP) or non-MPP, from 16 hospitals in Korea. Serological testing included chemiluminescence immunoassay (CLIA) and ELISA for detecting IgM and IgG, along with particle agglutination (PA) for total antibody measurements. Serological responses were analyzed at different times after symptom onset (0–4, 5–9, and 10–21 days). Results: Among 472 children with CAP (362 MPP, 110 non-MPP), 138 (29.2%) underwent PA testing, and 334 (70.8%) underwent IgM testing. PA at a 1:640 cutoff showed 48.0% sensitivity and 100% specificity. CLIA and ELISA showed comparable sensitivities (69.1% vs. 69.2%) and specificities (76.9% vs. 66.7%) for IgM testing. Seropositivity increased significantly with time since symptom onset (P for trend < 0.001), reaching 97.9% for IgM, 62.5% for IgG, and 94.7% for PA at 10–21 days. Conclusions The time post-symptom onset significantly influenced the diagnostic utility of serological tests for pediatric MPP, which showed limited value during the early stage of illness. These findings emphasize the importance of symptom onset-based interpretation of serological test results and their utility in complementing PCR when optimizing MPP diagnosis in children.

This study aimed to determine the prevalence of human epidermal growth factor receptor 2 (HER2)–ultralow breast cancer among cases initially classified as HER2 immunohistochemistry (IHC) 0 and assess interobserver variability in interpreting low-level HER2 expression. Methods: In this multicenter retrospective study, all invasive breast cancer cases diagnosed between January and December 2022 across 10 Korean institutions were retrieved. Institutional pathologists reexamined HER2 IHC slides originally reported as IHC 0 according to the 2018 American Society of Clinical Oncology/College of American Pathologists guidelines and reclassified them as HER2-null (0), HER2-ultralow (0+), or HER2-low (1+). Slides from 10% of HER2-null and HER2-ultralow cases were digitized for central review and independently assessed by two pathologists, with discrepancies resolved by consensus. Results: Among 8,026 cases, 2,836 cases (35.5%) were initially reported as IHC 0. Upon re-review, 1,673 (59.0%), 1,139 (40.2%), and 24 (0.8%) cases were reclassified as HER2-null, HER2-ultralow, and HER2-low, respectively. The prevalence of HER2-ultralow breast cancer varied considerably across institutions (23.7%–78.1%). Central review of 268 digitized cases showed concordance in 193 cases (72.0%). Among the 75 discordant cases, 54 tumors (72.0%) were upgraded from HER2-null to HER2-ultralow, and 18 (24.0%) tumors were upgraded from HER2-ultralow to HER2-low. Furthermore, two tumors (2.7%) were downgraded from HER2-ultralow to HER2-null. Conclusions: Approximately 40% of cases initially categorized as IHC 0 were reclassified as HER2-ultralow. The substantial inter-institutional variability observed in interpreting low-level HER2 expression highlights the need for standardized training and quality assurance to ensure accurate identification of patients eligible for HER2-targeted antibody–drug conjugates.

Purpose: The aim of this study is to compare the detection ability of quality of life (QoL) changes and responsiveness of the KOrean QUality of life in Stomach cancer patients Study group (KOQUSS)-40 and European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ). Materials and Methods: A multicenter prospective observational study was conducted to evaluate QoL changes after various gastrectomies between January 2021 and April 2022. Participants were instructed to complete the KOQUSS-40 and EORTC QLQ-C30/STO22 preoperatively and at 1, 3, 6, and 12 months postoperatively. QoL changes over time and QoL responsiveness were assessed for each questionnaire. Results: Data from 491 patients who underwent curative gastrectomy for gastric cancer at 22 institutions were analyzed. The summary scores of the KOQUSS-40 and EORTC QLQ-STO22 showed significant differences between the total and proximal gastrectomy groups (p=0.044 and p=0.038, respectively), but no difference was observed for the EORTC QLQ-C30. Dysphagia on the KOQUSS-40 was significantly different between the total and proximal gastrectomy groups (p=0.031); however, dysphagia on the EORTC QLQ-STO22 did not differ. The responsiveness of the KOQUSS-40 was similar to that of the EORTC QLQ in patients who experienced ≥ 10% body weight loss, but approximately 10% less in patients receiving adjuvant chemotherapy than the EORTC QLQ. Conclusion KOQUSS-40 has several advantages over EORTC QLQ-C30/STO22 when comparing QoL between the total and proximal gastrectomy groups. The findings provide information for researchers investigating the QoL of patients who have undergone curative gastrectomy for gastric cancer.

Background: The heterogeneity of chronic kidney disease (CKD) and fragmented analysis methods hinder the precise identification of novel biomarkers. We addressed this challenge using two independent cohorts to integrate genomics and metabolomics, aiming to identify cause-specific biomarkers for CKD in the Korean population. Methods: A longitudinal genome-wide association study using the Cox proportional hazards model was conducted using the Ansan and Ansung cohort. To validate these genomic biomarkers and integrate them with plasma metabolomics biomarkers, we utilized a hospital-based biopsy cohort to identify cause-specific CKD biomarkers. Within the biopsy cohort, we analyzed four disease subsets, including type 2 diabetic kidney disease (DKD), hypertensive nephropathy (HN), immunoglobulin A nephropathy (IgAN), and membranous nephropathy (MN), and compared them with healthy individuals. Significant single nucleotide polymorphisms(SNPs) and metabolites for each CKD subset were identified through logistic regression and correlation-based network analyses. Subsequently, we analyzed the risk of disease progression associated with the identified pairs. Results: A total of 448 variants associated with CKD occurrence were identified, with significant differences in several genetic variants and metabolites observed among patients with DKD, HN, IgAN, and MN compared to healthy individuals. Among 36 SNP-metabolite pairs, those involing FOXB1 and ZFP42 were associated with DKD, whereas pairs involving MMRN1 and SYNJ2 were linked to MN. Notably, the rs1025170 variant in FOXB1 and tyrosine pair was correlated with DKD progression. Conclusion Integrating genomics and metabolomics across independent cohorts enables the discovery of cause-specific biomarkers for the occurrence and progression of CKD in the Korean population.

Background: and Purpose The pain lateralization in cluster headache (CH) may be related to the asymmetry in the functions of the brain hemispheres. The right-sided dominance of pain in CH has been found inconsistently across studies, and so we aimed to characterize this and identify the factors influencing pain lateralization during current and previous bouts. Methods: This study enrolled 227 patients from the Korean Cluster Headache Registry between October 2018 and December 2020. We evaluated the side of pain during current and previous bouts, demographic features, and clinical characteristics, including handedness. Multivariable logistic regression analyses were performed to identify factors associated with the side of pain. Results: The 227 patients with CH included 131 (57.7%) with right-sided pain and 86 (37.9%) with left-sided pain during the current bout (p<0.001). The 189 patients with previous bouts of CH included 86.8% who consistently reported the same side of pain throughout multiple bouts (side-locked pain), with a higher prevalence of pain on the right than the left side (55.0% vs. 31.7%, p<0.001). Multivariable analyses revealed that higher age at diagnosis (odds ratio [OR]=1.045, p=0.031) and shorter CH attacks (OR=0.992, p=0.017) were associated with left-side-locked pain. However, handedness was not associated with the lateralization of leftside-locked pain. Conclusions This study has confirmed the predominance of right-sided pain throughout multiple CH bouts. We found that higher age at diagnosis and shorter CH attacks were associated with left-side-locked pain, suggesting that certain clinical factors are associated with the pain laterality. However, the underlying mechanisms linking these factors to lateralized pain remain unclear and therefore require further investigation.

Purpose: This study evaluated the postoperative quality of life (QoL) after various types of gastrectomy for gastric cancer. Materials and Methods: A multicenter prospective observational study was conducted in Korea using the Korean Quality of Life in Stomach Cancer Patients Study (KOQUSS)-40, a new QoL assessment tool focusing on postgastrectomy syndrome. Overall, 496 patients with gastric cancer were enrolled, and QoL was assessed at 5 time points: preoperatively and at 1, 3, 6, and 12 months after surgery. Results: Distal gastrectomy (DG) and pylorus-preserving gastrectomy (PPG) showed significantly better outcomes than total gastrectomy (TG) and proximal gastrectomy (PG) with regard to total score, indigestion, and dysphagia. DG, PPG, and TG also showed significantly better outcomes than PG in terms of dumping syndrome and worry about cancer. Postoperative QoL did not differ significantly according to anastomosis type in DG, except for Billroth I anastomosis, which achieved better bowel habit change scores than the others. No domains differed significantly when comparing double tract reconstruction and esophagogastrostomy after PG. The total QoL score correlated significantly with postoperative body weight loss (more than 10%) and extent of resection (P<0.05 for both).Reflux as assessed by KOQUSS-40 did not correlate significantly with reflux observed on gastroscopy 1 year postoperatively (P=0.064). Conclusions Our prospective observation using KOQUSS-40 revealed that DG and PPG lead to better QoL than TG and PG. Further study is needed to compare postoperative QoL according to anastomosis type in DG and PG.

Purpose: Since 1995, the Korean Gastric Cancer Association (KGCA) has been periodically conducting nationwide surveys on patients with surgically treated gastric cancer. This study details the results of the survey conducted in 2023. Materials and Methods: The survey was conducted from March to December 2024 using a standardized case report form. Data were collected on 86 items, including patient demographics, tumor characteristics, surgical procedures, and surgical outcomes. The results of the 2023 survey were compared with those of previous surveys. Results: Data from 12,751 cases were collected from 66 institutions. The mean patient age was 64.6 years, and the proportion of patients aged ≥71 years increased from 9.1% in 1995 to 31.7% in 2023. The proportion of upper-third tumors slightly decreased to 16.8% compared to 20.9% in 2019. Early gastric cancer accounted for 63.1% of cases in 2023.Regarding operative procedures, a totally laparoscopic approach was most frequently applied (63.2%) in 2023, while robotic gastrectomy steadily increased to 9.5% from 2.1% in 2014.The most common anastomotic method was the Billroth II procedure (48.8%) after distal gastrectomy and double-tract reconstruction (51.9%) after proximal gastrectomy in 2023.However, the proportion of esophago-gastrostomy with anti-reflux procedures increased to 30.9%. The rates of post-operative mortality and overall complications were 1.0% and 15.3%, respectively. Conclusions The results of the 2023 nationwide survey demonstrate the current status of gastric cancer treatment in Korea. This information will provide a basis for future gastric cancer research.