{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,25]],"date-time":"2026-06-25T05:46:26Z","timestamp":1782366386775,"version":"3.54.5"},"reference-count":11,"publisher":"Walter de Gruyter GmbH","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"abstract":"Abstract<\/jats:title>\n \n Objectives<\/jats:title>\n To analyze how diagnostic success was achieved in a challenging case of occult breast cancer using the SIDER protocol, a structured Safety-II framework for reflecting on successful diagnostic processes.<\/jats:p>\n <\/jats:sec>\n \n Case presentation<\/jats:title>\n A 56-year-old woman developed progressive pain extending from the right upper limb to the right periscapular region 8\u00a0weeks before presentation, followed by axillary pain, cutaneous changes, and lymphadenopathy. Cervical radiography, cervical magnetic resonance imaging, breast ultrasonography, and computed tomography did not identify a primary breast lesion. At presentation, the clinical team retained breast malignancy in the differential diagnosis because of the patient\u2019s sex, progressive symptoms, axillary lymphadenopathy, and unexplained clinical trajectory. Diagnostic uncertainty was explicitly discussed with the patient, supporting continued follow-up. Two weeks later, positron emission tomography\u2013computed tomography showed intense uptake from the right neck to the supraclavicular and axillary regions. Axillary lymph node biopsy demonstrated metastatic carcinoma with immunohistochemical findings consistent with breast origin, establishing the diagnosis of occult breast cancer.<\/jats:p>\n <\/jats:sec>\n \n Conclusions<\/jats:title>\n Applying the SIDER protocol showed that diagnostic progress depended on three reproducible processes: maintaining a low-probability but high-impact diagnosis despite nondiagnostic imaging, preserving patient engagement under uncertainty, and enabling diagnostic\u00a0re-entry through cross-specialty collaboration. This case extends the use of Safety-II reflection by demonstrating how structured analysis of diagnostic success can\u00a0generate practical lessons for complex, evolving presentations.<\/jats:p>\n <\/jats:sec>","DOI":"10.1515\/dx-2026-0057","type":"journal-article","created":{"date-parts":[[2026,6,25]],"date-time":"2026-06-25T04:55:52Z","timestamp":1782363352000},"source":"Crossref","is-referenced-by-count":0,"title":["Learning from what went right: a Safety-II application of the SIDER protocol to a case of occult breast cancer"],"prefix":"10.1515","author":[{"given":"Takako","family":"Kamei","sequence":"first","affiliation":[{"name":"Department of Diagnostic and Generalist Medicine , Dokkyo Medical University , Mibu , Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yuka","family":"Shimada","sequence":"additional","affiliation":[{"name":"Department of Diagnostic and Generalist Medicine , Dokkyo Medical University , Mibu , Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yu","family":"Shimura","sequence":"additional","affiliation":[{"name":"Department of Diagnostic and Generalist Medicine , Dokkyo Medical University , Mibu , Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yuna","family":"Sugawara","sequence":"additional","affiliation":[{"name":"Department of Diagnostic and Generalist Medicine , Dokkyo Medical University , Mibu , Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Riko","family":"Higashihara","sequence":"additional","affiliation":[{"name":"Department of Diagnostic and Generalist Medicine , Dokkyo Medical University , Mibu , Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Masashi","family":"Yokose","sequence":"additional","affiliation":[{"name":"Department of Diagnostic and Generalist Medicine , Dokkyo Medical University , Mibu , Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yukinori","family":"Harada","sequence":"additional","affiliation":[{"name":"Department of Diagnostic and Generalist Medicine , Dokkyo Medical University , Mibu , Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3788-487X","authenticated-orcid":false,"given":"Taro","family":"Shimizu","sequence":"additional","affiliation":[{"name":"Harvard Medical School , Boston , MA , USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"374","published-online":{"date-parts":[[2026,6,26]]},"reference":[{"key":"2026062504554515845_j_dx-2026-0057_ref_001","unstructured":"World Health Organization. Breast cancer [Internet]. Geneva: World Health Organization; 2025. https:\/\/www.who.int\/news-room\/fact-sheets\/detail\/breast-cancer [Accessed 9 Mar 2026]."},{"key":"2026062504554515845_j_dx-2026-0057_ref_002","doi-asserted-by":"crossref","unstructured":"Ofri, A, Moore, K. Occult breast cancer: where are we at? Breast 2020;54:211\u201315. https:\/\/doi.org\/10.1016\/j.breast.2020.10.012.","DOI":"10.1016\/j.breast.2020.10.012"},{"key":"2026062504554515845_j_dx-2026-0057_ref_003","doi-asserted-by":"crossref","unstructured":"Wang, R, Yang, HX, Chen, J, Huang, JJ, Lv, Q. Best treatment options for\u00a0occult breast cancer: a meta-analysis. Front Oncol 2023;13:1051232. https:\/\/doi.org\/10.3389\/fonc.2023.1051232.","DOI":"10.3389\/fonc.2023.1051232"},{"key":"2026062504554515845_j_dx-2026-0057_ref_004","unstructured":"Hollnagel, E. Safety-I and safety-II: the past and future of safety management. Farnham: Ashgate; 2014."},{"key":"2026062504554515845_j_dx-2026-0057_ref_005","doi-asserted-by":"crossref","unstructured":"Shimizu, T. Learning from what goes right: a safety II framework for improving diagnosis at the point of care. Diagnosis (Berl) 2025. published online July 17. https:\/\/doi.org\/10.1515\/dx-2025-0086.","DOI":"10.1515\/dx-2025-0086"},{"key":"2026062504554515845_j_dx-2026-0057_ref_006","doi-asserted-by":"crossref","unstructured":"Ni, YB, Tsang, JYS, Shao, MM, Chan, SK, Tong, J, To, KF, et al.. GATA-3 is superior to GCDFP-15 and mammaglobin to identify primary and metastatic breast cancer. Breast Cancer Res Treat 2018;169:25\u201332. https:\/\/doi.org\/10.1007\/s10549-017-4645-2.","DOI":"10.1007\/s10549-017-4645-2"},{"key":"2026062504554515845_j_dx-2026-0057_ref_007","doi-asserted-by":"crossref","unstructured":"Selves, J, Long-Mira, E, Mathieu, MC, Rochaix, P, Ili\u00e9, M. Immunohistochemistry for diagnosis of metastatic carcinomas of unknown primary site. 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Washington DC: National Academies Press;\u00a02015."}],"container-title":["Diagnosis"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.degruyterbrill.com\/document\/doi\/10.1515\/dx-2026-0057\/xml","content-type":"application\/xml","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/www.degruyterbrill.com\/document\/doi\/10.1515\/dx-2026-0057\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,6,25]],"date-time":"2026-06-25T04:56:03Z","timestamp":1782363363000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.degruyterbrill.com\/document\/doi\/10.1515\/dx-2026-0057\/html"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,6,26]]},"references-count":11,"alternative-id":["10.1515\/dx-2026-0057"],"URL":"https:\/\/doi.org\/10.1515\/dx-2026-0057","relation":{},"ISSN":["2194-8011","2194-802X"],"issn-type":[{"value":"2194-8011","type":"print"},{"value":"2194-802X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,6,26]]}}}