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The patient\u2019s DH led her parents to undergo genetic testing as well, and new carriers were found, highlighting the importance of genetic counselling and surveillance for the entire family. Due to the rarity of DH, cancer risk and optimal surveillance strategies are not addressed in current guidelines or other sources. This report summarises existing evidence and highlights the need for further research to better understand cancer risks and to develop effective management strategies for individuals with this unique genetic profile.<\/jats:p>","DOI":"10.1136\/bcr-2024-263687","type":"journal-article","created":{"date-parts":[[2025,4,22]],"date-time":"2025-04-22T15:20:20Z","timestamp":1745335220000},"page":"e263687","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":1,"title":["Double heterozygosity for <i>BRCA1<\/i> and <i>BRCA2<\/i> in breast cancer: considerations in surveillance and cancer risk management"],"prefix":"10.1136","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0009-0009-0191-2451","authenticated-orcid":false,"given":"Nonoko","family":"Wakaki","sequence":"first","affiliation":[{"name":"Breast Surgery, Japanese Red Cross Akita Hospital, Akita, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Tatsunori","family":"Shimoi","sequence":"additional","affiliation":[{"name":"Medical Oncology, National Cancer Center Hospital, Chuo-ku, Tokyo, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Shogo","family":"Nakamoto","sequence":"additional","affiliation":[{"name":"Okayama University Hospital, Okayama, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yuichiro","family":"Kikawa","sequence":"additional","affiliation":[{"name":"Breast Surgery, Kansai Medical University Hirakata Hospital, Hirakata, Osaka, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Aki","family":"Ito","sequence":"additional","affiliation":[{"name":"Breast Surgery, Japanese Red Cross Akita Hospital, Akita, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Takayuki","family":"Iwamoto","sequence":"additional","affiliation":[{"name":"Breast and Thyroid Surgery, Kawasaki Medical School Hospital, Kurashiki, Okayama, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"239","published-online":{"date-parts":[[2025,4,22]]},"reference":[{"key":"2025082802120631000_18.4.e263687.1","doi-asserted-by":"publisher","DOI":"10.1200\/JCO.2015.65.0747"},{"key":"2025082802120631000_18.4.e263687.2","doi-asserted-by":"crossref","DOI":"10.1038\/s41467-018-06581-8","article-title":"Germline pathogenic variants of 11 breast cancer genes in 7,051 Japanese patients and 11,241 controls","volume":"9","author":"Momozawa","year":"2018","journal-title":"Nat Commun"},{"key":"2025082802120631000_18.4.e263687.3","doi-asserted-by":"publisher","DOI":"10.1007\/s10549-012-2050-4"},{"key":"2025082802120631000_18.4.e263687.4","doi-asserted-by":"crossref","DOI":"10.1186\/s13058-016-0768-3","article-title":"Inheritance of deleterious mutations at both BRCA1 and BRCA2 in an international sample of 32,295 women","volume":"18","author":"Rebbeck","year":"2016","journal-title":"Breast Cancer Res"},{"key":"2025082802120631000_18.4.e263687.5","unstructured":"Japan hereditary breast and ovarian cancer comprehensive medical care system organization. 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