Purpose: Notable effectiveness of trastuzumab deruxtecan in patients with human epidermal growth factor receptor 2 (HER2)–low advanced breast cancer (BC) has focused pathologists’ attention. We studied the incidence and clinicopathologic characteristics of HER2-low BC, and the effects of immunohistochemistry (IHC) associated factors on HER2 IHC results. Materials and Methods: The Breast Pathology Study Group of the Korean Society of Pathologists conducted a nationwide study using real-world data on HER2 status generated between January 2022 and December 2022. Information on HER2 IHC protocols at each participating institution was also collected. Results: Total 11,416 patients from 25 institutions included in this study. Of these patients, 40.7% (range, 6.0% to 76.3%) were classified as HER2-zero, 41.7% (range, 10.5% to 69.1%) as HER2-low, and 17.5% (range, 6.7% to 34.0%) as HER2-positive. HER2-low tumors were associated with positive estrogen receptor and progesterone receptor statuses (p < 0.001 and p < 0.001, respectively). Antigen retrieval times (≥ 36 minutes vs. < 36 minutes) and antibody incubation times (≥ 12 minutes vs. < 12 minutes) affected on the frequency of HER2 IHC 1+ BC at institutions using the PATHWAY HER2 (4B5) IHC assay and BenchMark XT or Ultra staining instruments. Furthermore, discordant results between core needle biopsy and subsequent resection specimen HER2 statuses were observed in 24.1% (787/3,259) of the patients. Conclusion The overall incidence of HER2-low BC in South Korea concurs with those reported in previously published studies. Significant inter-institutional differences in HER2 IHC protocols were observed, and it may have impact on HER2-low status. Thus, we recommend standardizing HER2 IHC conditions to ensure precise patient selection for targeted therapy.

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.

The primary objective of initial treatment for thyroid cancer is minimizing treatment-related side effects and unnecessary interventions while improving patients’ overall and disease-specific survival rates, reducing the risk of disease persistence or recurrence, and conducting accurate staging and recurrence risk analysis. Appropriate surgical treatment is the most important requirement for this purpose, and additional treatments including radioactive iodine therapy and thyroid-stimulating hormone suppression therapy are performed depending on the patients’ staging and recurrence risk. Diagnostic surgery may be considered when repeated pathologic tests yield nondiagnostic results (Bethesda category 1) or atypia of unknown significance (Bethesda category 3), depending on clinical risk factors, nodule size, ultrasound findings, and patient preference. If a follicular neoplasm (Bethesda category 4) is diagnosed pathologically, surgery is the preferred option. For suspicious papillary carcinoma (suspicious for malignancy, Bethesda category 5), surgery is considered similar to a diagnosis of malignancy (Bethesda category 6). As for the extent of surgery, if the cancer is ≤1 cm in size and clinically free of extrathyroidal extension (ETE) (cT1a), without evidence of cervical lymph node (LN) metastasis (cN0), and without obvious reason to resect the contralateral lobe, a lobectomy can be performed. If the cancer is 1-2 cm in size, clinically free of ETE (cT1b), and without evidence of cervical LN metastasis (cN0), lobectomy is the preferred option. For patients with clinically evident ETE to major organs (cT4) or with cervical LN metastasis (cN1) or distant metastasis (M1), regardless of the cancer size, total thyroidectomy and complete cancer removal should be performed at the time of initial surgery. Active surveillance may be considered for adult patients diagnosed with low-risk thyroid papillary microcarcinoma. Endoscopic and robotic thyroidectomy may be performed for low-risk differentiated thyroid cancer when indicated, based on patient preference.

Background: The coronavirus disease 2019 (COVID-19) pandemic and the consequent social distancing period are thought to have influenced the incidence of osteoporotic fracture in various ways, but the exact changes have not yet been well elucidated. The purpose of this study was to investigate the impact of the COVID-19 pandemic on the incidence of osteoporotic fracture using a nationwide cohort. Methods: The monthly incidence rates of vertebral; hip; and non-vertebral, non-hip fractures were collected from a nationwide database of the Korean National Health Insurance Review and Assessment from July 2016 to June 2021. Segmented regression models were used to assess the change in levels and trends in the monthly incidence of osteoporotic fractures. Results: There was a step decrease in the incidence of vertebral fractures for both males (6.181 per 100,000, P=0.002) and females (19.299 per 100,000, P=0.006). However, there was a negative trend in the incidence of hip fracture among both males (-0.023 per 100,000 per month, P=0.023) and females (-0.032 per 100,000 per month, P=0.019). No impact of COVID-19-related social distancing was noted. Conclusions In conclusion, during the early days of the COVID-19 pandemic, vertebral fracture incidence considerably decreased with the implementation of social distancing measures.

Background: Conflicting evidence exists regarding the association between smoking and the risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We investigated the association between combustible cigarette (CC) smoking, noncombustible tobacco product (NCTP) use, and the use of any tobacco product with various coronavirus disease 2019 (COVID-19) outcomes. Methods: A case-control study was conducted using the Korea Disease Control and Prevention Agency-COVID19-National Health Insurance Service (NHIS) cohort. A retrospective cohort study was conducted using 12,571,698 individuals from the NHIS cohort. Logistic regression evaluated the association between CC smoking, NCTP use, and use of any tobacco product with SARS-CoV-2 infection. Poisson regression evaluated the association between these forms of tobacco product use and COVID-19-related hospitalization and mortality. Results: In the case-control study, we identified 30,878 cases of SARS-CoV-2 infection. The odds ratios (95% confidence intervals [CIs]) for SARS-CoV-2 infection were lower among current CC smokers (0.51, 0.48–0.54), current- and former-NCTP users (0.80, 0.74–0.88;0.82, 0.74–0.91), and current users of any tobacco product (0.52, 0.49–0.55) relative to never user controls. In retrospective cohort study, we identified 16,521 COVID-19-related hospitalization and 362 COVID-19-related deaths. The relative risks (95% CIs) for COVID-19-related hospitalization were lower among current CC smokers (0.51, 0.48–0.54) and current users of any tobacco product (0.53, 0.50–0.56) relative to never user controls. There was no association between the use of tobacco product and COVID-19-related mortality. Conclusion Current CC smokers and current users of any tobacco product showed reduced risk of SARS-CoV-2 infection and COVID-19-related hospitalization. It remains uncertain whether these relationships are causal.

Prolonged viral shedding of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in an immunocompromised host is a challenge as the treatment and infection control for chronic coronavirus disease 2019 infection is not well established and there is a potential risk of new variants emerging. A 48-year-old woman who underwent chemotherapy, including rituximab and steroid, had reactivation of SARS-CoV-2 68 days after the virus was first detected. She successfully recovered after receiving convalescent plasma and intravenous immunoglobulin. Genomic analysis demonstrated that viruses collected from the nasopharyngeal specimens at day 0 and day 68 had 18 different nucleotide mutations, implying within-host evolution after in-depth epidemiologic investigation.

Purpose: Although endovascular aneurysm repair (EVAR) has been shown to be superior to open surgical repair (OSR) for abdominal aortic aneurysm (AAA) treatment, no large-scale studies in the Korean population have compared outcomes and costs. Methods: The National Health Insurance Service database in Korea was screened to identify AAA patients treated with EVAR or OSR from 2008 to 2019. Perioperative, early postoperative, and long-term survival were compared, as were reinterventions and complications. Patients were followed-up through 2020. Results: Of the 13,631 patients identified, 2,935 underwent OSR and 10,696 underwent EVAR. Perioperative mortality rate was lower in the EVAR group (4.2% vs. 8.0%, P < 0.001) even after excluding patients with ruptured AAA (2.7% vs.3.3%, P = 0.003). However, long-term mortality rate per 100 person-years was significantly higher in the EVAR than in the OSR group (9.0 vs. 6.4, P < 0.001), and all-cause mortality was lower in the OSR group (hazard ratio, 0.9; 95% confidence interval, 0.87–0.97, P = 0.008). EVAR had a higher AAA-related reintervention rate per 100 person-years (1.75 vs. 0.52), and AAA-related reintervention costs were almost 10-fold higher with EVAR (US dollar [USD] 6,153,463) than with OSR (USD 624,216). Conclusion While EVAR may have short-term advantages, OSR may provide better long-term outcomes and costeffectiveness for AAA treatment in the Korean population, under the medical expense system in Korea.

Purpose: Renal tumors account for approximately 7% of all childhood cancers. These include Wilms tumor (WT), clear cell sarcoma of the kidney (CCSK), malignant rhabdoid tumor of the kidney (MRTK), renal cell carcinoma (RCC), congenital mesoblastic nephroma (CMN) and other rare tumors. We investigated the epidemiology of pediatric renal tumors in Korea. Materials and Methods: From January 2001 to December 2015, data of pediatric patients (0–18 years) newly-diagnosed with renal tumors at 26 hospitals were retrospectively analyzed. Results: Among 439 patients (male, 240), the most common tumor was WT (n=342, 77.9%), followed by RCC (n=36, 8.2%), CCSK (n=24, 5.5%), MRTK (n=16, 3.6%), CMN (n=12, 2.7%), and others (n=9, 2.1%). Median age at diagnosis was 27.1 months (range 0-225.5) and median follow-up duration was 88.5 months (range 0-211.6). Overall, 32 patients died, of whom 17, 11, 1, and 3 died of relapse, progressive disease, second malignant neoplasm, and treatment-related mortality. Five-year overall survival and event free survival were 97.2% and 84.8% in WT, 90.6% and 82.1% in RCC, 81.1% and 63.6% in CCSK, 60.3% and 56.2% in MRTK, and 100% and 91.7% in CMN, respectively (p < 0.001). Conclusion The pediatric renal tumor types in Korea are similar to those previously reported in other countries. WT accounted for a large proportion and survival was excellent. Non-Wilms renal tumors included a variety of tumors and showed inferior outcome, especially MRTK. Further efforts are necessary to optimize the treatment and analyze the genetic characteristics of pediatric renal tumors in Korea.

Background: Ruptured abdominal aortic aneurysm (rAAA) is a serious complication of abdominal aortic aneurysm associated with high operative mortality and morbidity rates. The present study evaluated the perioperative and long-term outcomes of Korean patients with rAAA based on national health insurance claims data. Methods: The National Health Insurance Service (NHIS) database was searched retrospectively to identify patients with rAAA who underwent endovascular aneurysm repair (EVAR) and open surgical repair (OSR) from 2009 to 2018. Perioperative (≤ 30 days), early postoperative (≤ 3 month), and long-term (> 3 month) survival, reinterventions, and complications were assessed. Results: The search identified 1,034 patients with rAAA, including 594 who underwent EVAR and 440 who underwent OSR. When the study period was divided into two, the total numbers of patients with rAAA, patients who underwent EVAR, and octogenarians were higher during the second half. The perioperative mortality rate was 29.8% in the EVAR and 35.0% in the OSR group (P = 0.028). Hartmann’s procedure for bowel infarction was performed more frequently in the OSR than in the EVAR group (adjusted odds ratio, 6.28; 95% confidence interval [CI], 2.33–21.84; P = 0.001), but other complication rates did not differ significantly. All-cause mortality during the entire observation period did not differ significantly in the EVAR and OSR groups (adjusted hazard ratio, 1.17; 95% CI, 0.98–1.41; P = 0.087). Abdominal aortic aneurysm-related reintervention rate was significantly lower in the OSR group (adjusted hazard ratio, 0.31; 95% CI, 0.14–0.70; P = 0.005). Conclusion Although EVAR showed somewhat superior perioperative outcomes for rAAA, the long-term outcomes of EVAR after excluding initial 3 months were significantly worse than OSR. When anatomically feasible for both treatments, the perioperative mortality risk and reasonable prospects of long-term survival should be considered in rAAA.

Purpose: The gene expression test (GET) was used to predict the response to chemotherapy and the recurrence risk.Several randomized clinical trials have demonstrated that some patients with node-positive disease can achieve favorable survival outcomes even without adjuvant chemotherapy. This study aimed to predict the results of Oncotype DX (Genomic Health) and MammaPrint (Agendia) using traditional clinicopathological factors. Methods: We reviewed the records of 311 patients who underwent GET for hormone receptor-positive/human epidermal growth factor receptor 2 (HER2)-negative primary invasive breast cancer with node-positive disease between 2015 and 2022 at Severance Hospital and Gangneung Asan Medical Center. Univariate and multivariate logistic regression analyses assessed the relationships between clinicopathological variables and risk stratification using the GET results. Results: A simple scoring system was created by assigning integer values to each variable. A score of 3 was assigned for histological grade 3, a score of 2 for pathologic T2 or above, and a score of 1 for a lower progesterone receptor (1–20 or Alled score 3–6), HER2 2-positive, and high Ki-67 (>20). In the validation cohort, overall accuracy was 0.798 (95% confidence interval, 0.744–0.844). Conclusion The high GET risk results can be predicted using traditional clinicopathological factors: tumor size, progesterone receptor, histological grade, HER2, and Ki-67. These results will be useful for treatment decision-making among clinically high-risk patients with HR-positive/HER2-negative and node-positive disease, helping to identify patients to whom the GET assay may not apply.