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<article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:ali="http://www.niso.org/schemas/ali/1.0/" article-type="research-article" dtd-version="1.2" xml:lang="en"><front><journal-meta><journal-id journal-id-type="publisher-id">Pediatric Hematology/Oncology and Immunopathology</journal-id><journal-title-group><journal-title xml:lang="en">Pediatric Hematology/Oncology and Immunopathology</journal-title><trans-title-group xml:lang="ru"><trans-title>Вопросы гематологии/онкологии и иммунопатологии в педиатрии</trans-title></trans-title-group></journal-title-group><issn publication-format="print">1726-1708</issn><issn publication-format="electronic">2414-9314</issn><publisher><publisher-name xml:lang="en">Fund Doctors, Innovations, Science for Children</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="publisher-id">1076</article-id><article-id pub-id-type="doi">10.24287/j.1076</article-id><article-categories><subj-group subj-group-type="toc-heading" xml:lang="en"><subject>CLINICAL OBSERVATIONS</subject></subj-group><subj-group subj-group-type="toc-heading" xml:lang="ru"><subject>КЛИНИЧЕСКИЕ НАБЛЮДЕНИЯ</subject></subj-group><subj-group subj-group-type="article-type"><subject>Research Article</subject></subj-group></article-categories><title-group><article-title xml:lang="en">Mosaic Li–Fraumeni syndrome in acute lymphoblastic leukemia</article-title><trans-title-group xml:lang="ru"><trans-title>Мозаичная форма синдрома Ли–Фраумени при остром лимфобластном лейкозе</trans-title></trans-title-group></title-group><contrib-group><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0002-1085-4646</contrib-id><name-alternatives><name xml:lang="en"><surname>Kazakova</surname><given-names>A. N.</given-names></name><name xml:lang="ru"><surname>Казакова</surname><given-names>А. Н.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><email>albert.itov@dgoi.ru</email><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0009-0004-5464-3818</contrib-id><name-alternatives><name xml:lang="en"><surname>Kozeev</surname><given-names>V. A.</given-names></name><name xml:lang="ru"><surname>Козеев</surname><given-names>В. А.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><email>albert.itov@dgoi.ru</email><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0009-0003-3441-6397</contrib-id><name-alternatives><name xml:lang="en"><surname>Iliasova</surname><given-names>K. R.</given-names></name><name xml:lang="ru"><surname>Ильясова</surname><given-names>К. Р.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><email>albert.itov@dgoi.ru</email><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0009-0007-2614-9654</contrib-id><name-alternatives><name xml:lang="en"><surname>Dzhumagazieva</surname><given-names>D. S.</given-names></name><name xml:lang="ru"><surname>Джумагазиева</surname><given-names>Д. С.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><email>albert.itov@dgoi.ru</email><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0009-0000-1239-4068</contrib-id><name-alternatives><name xml:lang="en"><surname>Azatyan</surname><given-names>A. S.</given-names></name><name xml:lang="ru"><surname>Азатян</surname><given-names>А. С.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><email>albert.itov@dgoi.ru</email><xref ref-type="aff" rid="aff2"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0001-5201-6475</contrib-id><name-alternatives><name xml:lang="en"><surname>Abugova</surname><given-names>Y. G.</given-names></name><name xml:lang="ru"><surname>Абугова</surname><given-names>Ю. Г.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><email>albert.itov@dgoi.ru</email><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0001-7652-7704</contrib-id><name-alternatives><name xml:lang="en"><surname>Ilyushina</surname><given-names>M. A.</given-names></name><name xml:lang="ru"><surname>Илюшина</surname><given-names>М. А.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><email>albert.itov@dgoi.ru</email><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0003-1216-817X</contrib-id><name-alternatives><name xml:lang="en"><surname>Klimentova</surname><given-names>M. A.</given-names></name><name xml:lang="ru"><surname>Климентова</surname><given-names>М. А.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><email>albert.itov@dgoi.ru</email><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0003-0520-5630</contrib-id><name-alternatives><name xml:lang="en"><surname>Shelikhova</surname><given-names>L. N.</given-names></name><name xml:lang="ru"><surname>Шелихова</surname><given-names>Л. Н.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><email>albert.itov@dgoi.ru</email><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0002-1873-3486</contrib-id><name-alternatives><name xml:lang="en"><surname>Osipova</surname><given-names>E. Y.</given-names></name><name xml:lang="ru"><surname>Осипова</surname><given-names>Е. Ю.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><email>albert.itov@dgoi.ru</email><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0002-3793-104X</contrib-id><name-alternatives><name xml:lang="en"><surname>Lagoyko</surname><given-names>S. N.</given-names></name><name xml:lang="ru"><surname>Лагойко</surname><given-names>С. Н.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><email>albert.itov@dgoi.ru</email><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0001-9634-5828</contrib-id><name-alternatives><name xml:lang="en"><surname>Zerkalenkova</surname><given-names>E. A.</given-names></name><name xml:lang="ru"><surname>Зеркаленкова</surname><given-names>Е. А.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><email>albert.itov@dgoi.ru</email><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0003-0098-919X</contrib-id><name-alternatives><name xml:lang="en"><surname>Itov</surname><given-names>A. B.</given-names></name><name xml:lang="ru"><surname>Итов</surname><given-names>А. Б.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><email>albert.itov@dgoi.ru</email><xref ref-type="aff" rid="aff1"/></contrib></contrib-group><aff-alternatives id="aff1"><aff><institution xml:lang="en">The Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology of Ministry of Healthcare of the Russian Federation</institution></aff><aff><institution xml:lang="ru">ФГБУ «Национальный медицинский исследовательский центр детской гематологии, онкологии и иммунологии им. Дмитрия Рогачева» Минздрава России</institution></aff></aff-alternatives><aff-alternatives id="aff2"><aff><institution xml:lang="en">The N.I. Pirogov Russian National Research Medical University of Ministry of Healthcare of the Russian Federation</institution></aff><aff><institution xml:lang="ru">ФГАОУ ВО «Российский национальный исследовательский медицинский университет им. Н.И. Пирогова» Минздрава России</institution></aff></aff-alternatives><pub-date date-type="pub" iso-8601-date="2026-04-14" publication-format="electronic"><day>14</day><month>04</month><year>2026</year></pub-date><volume>25</volume><issue>1</issue><issue-title xml:lang="en"/><issue-title xml:lang="ru"/><fpage>158</fpage><lpage>165</lpage><history><date date-type="received" iso-8601-date="2026-01-30"><day>30</day><month>01</month><year>2026</year></date><date date-type="accepted" iso-8601-date="2026-03-05"><day>05</day><month>03</month><year>2026</year></date></history><permissions><copyright-statement xml:lang="en">Copyright ©; 2026, «D. Rogachev NMRCPHOI»</copyright-statement><copyright-statement xml:lang="ru">Copyright ©; 2026, ФГБУ «НМИЦ ДГОИ им. Дмитрия Рогачева» Минздрава России</copyright-statement><copyright-year>2026</copyright-year><copyright-holder xml:lang="en">«D. Rogachev NMRCPHOI»</copyright-holder><copyright-holder xml:lang="ru">ФГБУ «НМИЦ ДГОИ им. Дмитрия Рогачева» Минздрава России</copyright-holder><ali:free_to_read xmlns:ali="http://www.niso.org/schemas/ali/1.0/"/><license><ali:license_ref xmlns:ali="http://www.niso.org/schemas/ali/1.0/">https://creativecommons.org/licenses/by/4.0</ali:license_ref></license></permissions><self-uri xlink:href="https://hemoncim.com/jour/article/view/1076">https://hemoncim.com/jour/article/view/1076</self-uri><abstract xml:lang="en"><p>Li–Fraumeni syndrome (LFS) is a rare autosomal dominant tumor predisposition syndrome with high penetrance. The pathogenesis of the syndrome involves germline pathogenic variants in the <italic>TP53</italic> gene. The spectrum of cancers in LFS predominantly includes solid tumors, with hematologic malignancies occurring in only 4% of cancer diagnoses. Most patients have a family history of the disease, however, in 10–20% of cases, germline variants are <italic>de novo</italic>. The introduction of next generation sequencing into clinical practice has made it possible to describe rare cases of mosaic LFS syndrome in some patients with solid tumors. This article presents the first described clinical case of mosaic LFS in a patient with hematologic malignancy. This case demonstrates how detailed molecular genetic testing using modern diagnostic techniques can determine the true origin of a pathogenic variant in the <italic>TP53</italic> gene. The results of treatment show that, despite existing therapeutic options, patients with hematologic malignancies and LFS, including mosaic LFS, represent a challenging therapeutic group requiring the development of specialized treatment protocols.</p></abstract><trans-abstract xml:lang="ru"><p>Синдром Ли–Фраумени (СЛФ) – редкий аутосомно-доминантный синдром предрасположенности к опухолям, имеющий высокую пенетрантность. В его патогенезе лежат герминальные патогенные варианты в гене <italic>ТР53</italic>. Спектр опухолей при СЛФ представлен в основном солидными опухолями, онкогематологические заболевания встречаются всего в 4% случаев. Большинство пациентов имеют семейный анамнез заболевания, однако в 10–20% случаев герминальные варианты имеют характер <italic>de novo</italic>. Внедрение в практику высокопроизводительного секвенирования позволило описать у некоторых пациентов с солидными опухолями редкие мозаичные формы синдрома СЛФ. В работе представлен первый клинический случай мозаичной формы СЛФ при онкогематологическом заболевании. Этот случай демонстрирует, как тщательное молекулярно-генетическое обследование с использованием современных методов диагностики позволяет определить истинное происхождение патогенного варианта в гене <italic>TP53</italic>. Результаты лечения показывают, что, несмотря на существующие терапевтические возможности, онкогематологические пациенты с СЛФ, включая мозаичные формы, представляют собой сложную терапевтическую группу, для которой необходима разработка специализированных протоколов лечения.</p></trans-abstract><kwd-group xml:lang="en"><kwd>Li–Fraumeni syndrome</kwd><kwd>mosaic mutation</kwd><kwd>TP53</kwd><kwd>acute leukemia</kwd><kwd>next generation sequencing</kwd><kwd>CAR-T</kwd><kwd>hematopoietic stem cell transplantation</kwd></kwd-group><kwd-group xml:lang="ru"><kwd>синдром Ли–Фраумени</kwd><kwd>мозаичная форма мутации</kwd><kwd>ТР53</kwd><kwd>острый лейкоз</kwd><kwd>высокопроизводительное секвенирование</kwd><kwd>CAR-T</kwd><kwd>трансплантация гемопоэтических стволовых клеток</kwd></kwd-group><funding-group/></article-meta></front><body></body><back><ref-list><ref id="B1"><label>1.</label><mixed-citation>Kamihara J., Rana H.Q., Garber J.E. 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