Journal of Pathology and Translational Medicine

Original Article

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 PDF 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.

Review

Cervical intraepithelial neoplasia and cervical cytology in pregnancy: Ji-Young Kim, Jeong Yun Shim; J Pathol Transl Med. 2024;58(6):283-290. Published online November 7, 2024; DOI: https://doi.org/10.4132/jptm.2024.10.17

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Cervical cancer screening during pregnancy presents unique challenges for cytologic interpretation. This review focuses on pregnancy-associated cytomorphological changes and their impact on diagnosis of cervical intraepithelial neoplasia (CIN) and cervical cancer. Pregnancy-induced alterations include navicular cells, hyperplastic endocervical cells, immature metaplastic cells, and occasional decidual cells or trophoblasts. These changes can mimic abnormalities such as koilocytosis, adenocarcinoma in situ, and high-grade squamous intraepithelial lesions, potentially leading to misdiagnosis. Careful attention to nuclear features and awareness of pregnancy-related changes are crucial for correct interpretation. The natural history of CIN during pregnancy shows higher regression rates, particularly for CIN 2, with minimal risk of progression. Management of abnormal cytology follows modified risk-based guidelines to avoid invasive procedures, with treatment typically deferred until postpartum. The findings reported in this review emphasize the importance of considering pregnancy status in cytological interpretation, highlight potential problems, and provide guidance on differentiating benign pregnancy-related changes from true abnormalities. Understanding these nuances is essential for accurate diagnosis and proper management of cervical abnormalities in pregnant women.

Citations

Citations to this article as recorded by

HPV in Pregnancy: Implications for Screening, Vaccination, and Maternal–Fetal Health
Suman Kumar, Swati, Swati Salila, Akanksha Raj, Pratima Gupta, Neha Sharad, Nidhi Chaudhary
Journal of Pregnancy.2026;[Epub] CrossRef
The significance of biological samples from pregnant women in cervical intraepithelial neoplasia
Xue Mi, Maharjan Rashmi, Zangyu Pan, Di Wu, Jinwei Miao
Frontiers in Medicine.2025;[Epub] CrossRef
Oncologic and pregnancy outcomes of cervical high-grade intraepithelial lesions and delivery mode
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Brief Case Report

Multifocal Polypoid Endometriosis Mimicking Malignancy in a Young Woman with a History of Hormonal Treatment: Ji-Young Kim, Tae-Jong Song, Hye-Kyung Choi, Jeong Yun Shim; J Pathol Transl Med. 2015;49(5):418-420. Published online June 9, 2015; DOI: https://doi.org/10.4132/jptm.2015.05.12

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Citations

Citations to this article as recorded by

The Baffling Diagnosis of a Rare Case of Polypoid Endometriosis: Neoplasm Mimicking in a Young Pregnant Woman—A Case Report and Literature Review
Nicolae Gică, Ioana-Stefania Bostan, George-Dumitru Gheoca, Raluca Chirculescu, Alexandru-Gabriel Bran, Anca Maria Panaitescu, Claudia Mehedințu
Diagnostics.2025; 15(19): 2460. CrossRef
Fertility preservation of polypoid endometriosis: Case series and literature review
Sayuri Miyoshi, Ken Yamaguchi, Yoshitsugu Chigusa, Masumi Sunada, Koji Yamanoi, Akihito Horie, Junzo Hamanishi, Eiji Kondoh, Masaki Mandai
Journal of Obstetrics and Gynaecology Research.2022; 48(2): 502. CrossRef
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FUKUSHIMA JOURNAL OF MEDICAL SCIENCE.2022; 68(3): 183. CrossRef
Polypoid endometriosis: a mimic of malignancy
Soleen Ghafoor, Yulia Lakhman, Kay J. Park, Iva Petkovska
Abdominal Radiology.2020; 45(6): 1776. CrossRef

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