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- Prevalence of HER2-ultralow breast cancer in South Korea: a multicenter study by reassessment of HER2-zero cases
- Min Chong Kim, Eun Yoon Cho, Hee Jin Lee, Ji Shin Lee, Jee Yeon Kim, Wan Seop Kim, Chungyeul Kim, Sun-Young Jun, Hye Jeong Choi, So Mang Lee, Ahrong Kim, Ji-Young Kim, Jeong Yun Shim, Gyungyub Gong, Young Kyung Bae
- J Pathol Transl Med. 2026;60(2):184-192. Published online February 23, 2026
- DOI: https://doi.org/10.4132/jptm.2025.10.22
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Abstract
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Supplementary Material - Background
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.
- Early Colorectal Epithelial Neoplasm in Korea: A Multicenter Survey of Pathologic Diagnosis
- Yun Kyung Kang, So-Young Jin, Mee Soo Chang, Jung Yeon Kim, Gyeong Hoon Kang, Hye Seung Lee, Jin Hee Sohn, Ho Sung Park, Kye Won Kwon, Mi Jin Gu, Young Hee Maeng, Jong Eun Joo, Haeng Ji Kang, Hee Kyung Kim, Kee-Taek Jang, Mi Ja Lee, Hee Kyung Chang, Joon Mee Kim, Hye Seung Han, Won Ae Lee, Yoon Jung Choi, Dong Wook Kang, Sunhoo Park, Jae Hyuk Lee, Mee-Yon Cho
- Korean J Pathol. 2013;47(3):245-251. Published online June 25, 2013
- DOI: https://doi.org/10.4132/KoreanJPathol.2013.47.3.245
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Background The incidence of early colorectal epithelial neoplasm (ECEN) is increasing, and its pathologic diagnosis is important for patient care. We investigated the incidence of ECEN and the current status of its pathologic diagnosis.
Methods We collected datasheets from 25 institutes in Korea for the incidence of colorectal adenoma with high grade dysplasia (HGD) and low grade dysplasia in years 2005, 2007, and 2009; and early colorectal carcinoma in the year 2009. We also surveyed the diagnostic terminology of ECEN currently used by the participating pathologists.
Results The average percentage of diagnoses of adenoma HGD was 7.0%, 5.0%, and 3.4% in years 2005, 2007, and 2009, respectively. The range of incidence rates of adenoma HGD across the participating institutes has gradually narrowed over the years 2005 to 2009. The incidence rate of early colorectal carcinoma in the year 2009 was 21.2%. The participants did not share a single criterion or terminology for the diagnosis of adenoma HGD. The majority accepted the diagnostic terms that distinguished noninvasive, mucosal confined, and submucosal invasive carcinoma.
Conclusions Further research requirements suggested are a diagnostic consensus for the histopathologic diagnosis of ECEN; and standardization of diagnostic terminology critical for determining the disease code.
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- Diminutive and Small Colorectal Polyps: The Pathologist's Perspective
Yun Kyung Kang
Clinical Endoscopy.2014; 47(5): 404. CrossRef
- Diminutive and Small Colorectal Polyps: The Pathologist's Perspective
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