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.

Background: This retrospective observational matched-cohort study of 2,151,216 individuals from the Korean coronavirus disease 2019 (COVID-19) vaccine effectiveness cohort aimed to evaluate the comparative effectiveness of the COVID-19 bivalent versus monovalent vaccines in providing additional protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, critical infection, and death in Korea. Methods: Among individuals, those vaccinated with COVID-19 bivalent vaccines were matched in a 1:1 ratio with those who were vaccinated with monovalent vaccines (bivalent vaccines non-recipients) during the observation period. We fitted a time-dependent Cox proportional-hazards model to estimate hazard ratios (HRs) of COVID-19 outcomes for infection, critical infection, and death, and we defined vaccine effectiveness (VE) as 1–HR. Results: Compared with the bivalent vaccination group, the incidence proportions in the monovalent vaccination group were approximately three times higher for infection, nine times higher for critical infection, and 11 times higher for death. In the early stage of bivalent vaccination, relative VE of bivalent vaccine against monovalent vaccine was 42.4% against SARS-CoV-2 infection, 81.3% against critical infection, and 85.3% against death. In addition, VE against critical infection and death according to the elapsed period after bivalent vaccination was maintained at > 70%. Conclusion The bivalent booster dose provided additional protection against SARS-CoV-2 infections, critical infections, and deaths during the omicron variant phase of the COVID-19 pandemic.

Background/Aims: Although the incidence of nontuberculous mycobacteria pulmonary disease (NTM-PD), a chronic infectious disease, is increasing, lung and gut microbiota dysbiosis in NTM patients has rarely been studied and was therefore the focus of this study. Methods: We analyzed the microbiota diversity in sputum and stool samples from 10 healthy subjects and 10 patients with NTM-PD through sequencing of the V3 and V4 regions of the 16S rRNA gene. In NTM-PD patients, we comparatively evaluated the microbiota diversity according to the body mass index (BMI), with BMI ≤ 18.5 kg/m2 defined as “underweight” and BMI > 18.5 kg/m2 as “others.” Results: The sputum microbiota from NTM-PD patients tended to have lower index values of amplicon sequence variant richness, Shannon evenness, and beta diversity than those from the control group. Furthermore, NTM-PD patients with a low BMI had a lower microbiota diversity than patients with high BMI. Fecal samples from NTM-PD patients also significantly differed in alpha and beta diversity compared with the control group and exhibited a diversity pattern similar to that found in sputum samples. Conclusions Our results reveal that the lung and gut microbiota of patients with NTM-PD exhibit an altered distribution and reduced richness and diversity.

Background/Aims: Acute upper gastrointestinal (UGI) bleeding is a significant emergency situation with a mortality rate of 2% to 10%. Therefore, initial risk stratification is important for proper management. We aimed to evaluate the role of contrast-enhanced multidetector computed tomography (MDCT) for risk stratification in patients with acute UGI bleeding in the emergency room (ER). Methods: This retrospective study included patients with UGI bleeding in the ER. Glasgow-Blatchford risk score-computed tomography (GBS-CT) was assessed using a combination of GBS and the MDCT scan scoring system. Results: Of the 297 patients with UGI bleeding, 124 (41.8%) underwent abdominal MDCT. Among them, 90.3% were classified as high-risk by GBS, and five patients died (4.0%). Rebleeding occurred in nine patients (7.3%). The high-risk GBS-CT group had significantly higher in-hospital mortality (10.5% in high-risk vs. 1.4% in moderate risk vs. 0% in low-risk, p = 0.049), transfusion amount (p < 0.001), and endoscopic hemostasis (p < 0.001) compared to the moderate- and low-risk groups. Conclusions Adding MDCT scans to the existing validated prognosis model when predicting the risk of UGI bleeding in patients in the ER plays a significant role in determining in-hospital mortality, transfusions, and the need for endoscopic hemostasis.

Background: Despite the advances in neonatology, the incidence of bronchopulmonary dysplasia (BPD) is increasing. It is important to prevent the development of BPD in the first place. The online BPD outcome estimator from National Institute of Children Health and Human Development and Neonatal Research Network is available. However, it is not applicable for Asians. Moreover, limits are set for birth weight and gestational weeks excluding those who may still have BPD. The aim of this study was to develop a prediction model for BPD using first hour perinatal and neonatal factors in Korean very low birth weight infants (VLBWIs). Methods: Data were collected for 8,022 VLBWIs with gestational age (GA) ≥ 22 weeks who were born between January 1, 2013 and December 31, 2016, and admitted to the neonatal intensive care units of the KNN. Multiple logistic regression models reanalyzed by stepwise selection with significant clinical indicators for BPD. PROC package was used to calculate the area under curve (AUC) and corresponding 95% confidence intervals. Moreover, it was used to search the best cut-off value. External validation was performed with the 2017 Korean neonatal network (KNN) data. Results: After all missing data were excluded, 4,600 VLBWIs were included in the training dataset of the prediction model. Predictability of presence of BPD was 90.8% and prediction P value cut off was 0.550. Five-minute Apgar score, birth weight, GA, sex, surfactant use were significant indicators. Predictability of severe BPD was 81.5% and prediction P value cut off was 0.160. Five-minute Apgar score, birth weight, maternal PIH, chronic maternal hypertension, GA, sex, respiratory distress syndrome, need of resuscitation at birth were significant indicators. After external validation, sensitivity and specificity did not change significantly. Conclusion From this study, high predictability was obtained using clinical parameters obtained within one hour of life. P value for prediction of each grade of BPD and equation for calculation was presented. It can be helpful for the early prediction of BPD in Korean VLBWI. This study will contribute to the prediction of BPD in Asians especially Korean VLBWIs, not currently included in the NICHD BPD online BPD predictor. In addition, the predictive power may be continuously increased with the cumulative data of KNN.

Idiopathic spontaneous intraperitoneal hemorrhage is both rare and potentially fatal. The incidence of gastroepiploic artery rupture, especially a non-aneurysmal rupture, is extremely low. We report the case of an elderly woman who was mistakenly diagnosed with procedure-related bleeding after gastroscopy. A 0.3 cm polyp was identified and removed during the procedure. The patient later developed shock due to which gastroscopy was repeated; however, no unusual findings were observed. Therefore, abdominopelvic computerized tomography was performed and gastroepiploic artery rupture was detected. Transcatheter arterial embolization was immediately performed without laparotomy, without any complications. The bleeding was controlled, and the patient was discharged after embolization. It is important to acknowledge the possibility of spontaneous rupture of the visceral arteries in elderly individuals with hypertension or atherosclerosis, especially in the event of sudden abdominal pain or shock immediately after an endoscopic procedure. This is the first case report of idiopathic spontaneous rupture of the right gastroepiploic artery successfully managed by transcatheter arterial embolization in South Korea.

Idiopathic spontaneous intraperitoneal hemorrhage is both rare and potentially fatal. The incidence of gastroepiploic artery rupture, especially a non-aneurysmal rupture, is extremely low. We report the case of an elderly woman who was mistakenly diagnosed with procedure-related bleeding after gastroscopy. A 0.3 cm polyp was identified and removed during the procedure. The patient later developed shock due to which gastroscopy was repeated; however, no unusual findings were observed. Therefore, abdominopelvic computerized tomography was performed and gastroepiploic artery rupture was detected. Transcatheter arterial embolization was immediately performed without laparotomy, without any complications. The bleeding was controlled, and the patient was discharged after embolization. It is important to acknowledge the possibility of spontaneous rupture of the visceral arteries in elderly individuals with hypertension or atherosclerosis, especially in the event of sudden abdominal pain or shock immediately after an endoscopic procedure. This is the first case report of idiopathic spontaneous rupture of the right gastroepiploic artery successfully managed by transcatheter arterial embolization in South Korea.

Background: Despite the advances in neonatology, the incidence of bronchopulmonary dysplasia (BPD) is increasing. It is important to prevent the development of BPD in the first place. The online BPD outcome estimator from National Institute of Children Health and Human Development and Neonatal Research Network is available. However, it is not applicable for Asians. Moreover, limits are set for birth weight and gestational weeks excluding those who may still have BPD. The aim of this study was to develop a prediction model for BPD using first hour perinatal and neonatal factors in Korean very low birth weight infants (VLBWIs). Methods: Data were collected for 8,022 VLBWIs with gestational age (GA) ≥ 22 weeks who were born between January 1, 2013 and December 31, 2016, and admitted to the neonatal intensive care units of the KNN. Multiple logistic regression models reanalyzed by stepwise selection with significant clinical indicators for BPD. PROC package was used to calculate the area under curve (AUC) and corresponding 95% confidence intervals. Moreover, it was used to search the best cut-off value. External validation was performed with the 2017 Korean neonatal network (KNN) data. Results: After all missing data were excluded, 4,600 VLBWIs were included in the training dataset of the prediction model. Predictability of presence of BPD was 90.8% and prediction P value cut off was 0.550. Five-minute Apgar score, birth weight, GA, sex, surfactant use were significant indicators. Predictability of severe BPD was 81.5% and prediction P value cut off was 0.160. Five-minute Apgar score, birth weight, maternal PIH, chronic maternal hypertension, GA, sex, respiratory distress syndrome, need of resuscitation at birth were significant indicators. After external validation, sensitivity and specificity did not change significantly. Conclusion From this study, high predictability was obtained using clinical parameters obtained within one hour of life. P value for prediction of each grade of BPD and equation for calculation was presented. It can be helpful for the early prediction of BPD in Korean VLBWI. This study will contribute to the prediction of BPD in Asians especially Korean VLBWIs, not currently included in the NICHD BPD online BPD predictor. In addition, the predictive power may be continuously increased with the cumulative data of KNN.

Purpose: The aim of this study was to evaluate the physiological and behavioral effects of auditory stimulation with their own parent’s voice on heart rate and sleep states of very-low-birth-weight infants (VLBWIs) in neonatal intensive care unit. Methods: The data of 28 VLBWIs at the Ewha Womans University Mokdong Hospital between October 2016 and May 2017 was analyzed. They were exposed to sounds similar to those of mothers’ heartbeat they had heard in the uterus and their own parent’s voice. Heart rate was assessed as the physiological responses and sleep state of infants as behavioral response. The sleep states were categorized into six states. The music intervention program was provided twice a week. Results: Twenty-eight babies with an average gestational age of 28 weeks (average birth weight of 1.09 kg) had undergone the sessions (average of 16 times) average of 16 times. During the initial period, there were no meaningful differences of the heart rates measured by the physiological functions before and after the sessions. However, as we move to the adaptive phase, the average heart rate was 156.96±12.22, and the pre-discharge was 149.11±12.01, which indicates meaningful differences (P<0.05). Infants’ behavioral function was statistically insignificant. Conclusion The music intervention techniques in the neonatal intensive care unit environment in Korea have provided positive influence to VLBWIs' physiological reactions. We were not able to come up with the relevant indicators during this phase of the study but we do plan to announce the future study results after indexing the observation results.

Purpose: The aim of this study was to evaluate the physiological and behavioral effects of auditory stimulation with their own parent’s voice on heart rate and sleep states of very-low-birth-weight infants (VLBWIs) in neonatal intensive care unit. Methods: The data of 28 VLBWIs at the Ewha Womans University Mokdong Hospital between October 2016 and May 2017 was analyzed. They were exposed to sounds similar to those of mothers’ heartbeat they had heard in the uterus and their own parent’s voice. Heart rate was assessed as the physiological responses and sleep state of infants as behavioral response. The sleep states were categorized into six states. The music intervention program was provided twice a week. Results: Twenty-eight babies with an average gestational age of 28 weeks (average birth weight of 1.09 kg) had undergone the sessions (average of 16 times) average of 16 times. During the initial period, there were no meaningful differences of the heart rates measured by the physiological functions before and after the sessions. However, as we move to the adaptive phase, the average heart rate was 156.96±12.22, and the pre-discharge was 149.11±12.01, which indicates meaningful differences (P<0.05). Infants’ behavioral function was statistically insignificant. Conclusion The music intervention techniques in the neonatal intensive care unit environment in Korea have provided positive influence to VLBWIs' physiological reactions. We were not able to come up with the relevant indicators during this phase of the study but we do plan to announce the future study results after indexing the observation results.