{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,8]],"date-time":"2026-07-08T05:16:25Z","timestamp":1783487785142,"version":"3.55.0"},"reference-count":21,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,7,8]],"date-time":"2026-07-08T00:00:00Z","timestamp":1783468800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Oncol."],"abstract":"<jats:p>\n                    Mast cell leukemia (MCL), the most aggressive and often fatal subtype of systemic mastocytosis, is predominantly driven by\n                    <jats:italic>KIT<\/jats:italic>\n                    mutations, with the\n                    <jats:italic>KIT<\/jats:italic>\n                    p.D816V mutation being the most prevalent. Rare noncanonical\n                    <jats:italic>KIT<\/jats:italic>\n                    mutations remain poorly characterized, particularly when combined with a CD25\u2212negative immunophenotype and high\u2212risk cytogenetics. Through this case report, we aimed to enrich the molecular spectrum of MCL, emphasize the value of integrated diagnosis, and provide a reference for individualized treatment of older patients with high-risk MCL. This case involves an 81\u2212year\u2212old woman, with aleukemic MCL, who presented with dizziness and back pain. Severe pancytopenia was present, with 3% of atypical mast cells in the peripheral blood and 69.5% of abnormal mast cells in the bone marrow. Flow cytometry revealed a unique CD117\n                    <jats:sup>bri<\/jats:sup>\n                    , CD9\n                    <jats:sup>bri<\/jats:sup>\n                    , CD203c\n                    <jats:sup>+<\/jats:sup>\n                    , CD2\n                    <jats:sup>+<\/jats:sup>\n                    , CD25\n                    <jats:sup>-<\/jats:sup>\n                    , and HLA\u2212DR\n                    <jats:sup>-<\/jats:sup>\n                    immunophenotypes. Karyotyping revealed complex clonal abnormalities, including monosomy 7. Next\u2212generation sequencing identified a rare activating\n                    <jats:italic>KIT<\/jats:italic>\n                    p.V559G mutation (variant allele frequency, 42%), which is uncommon in MCL. Despite advanced age, life\u2212threatening complications (sepsis, gastrointestinal bleeding, and myocardial infarction), and dismal prognostic features, the patient achieved clinical improvement with partial hematologic recovery on low\u2212dose imatinib plus intensive supportive care and remained stable without evidence of disease progression during a four month follow-up period. This case represents a rare instance of aleukemic MCL cases with a\n                    <jats:italic>KIT<\/jats:italic>\n                    p.V559G mutation, CD25 negativity, and a complex karyotype, underscoring the importance of a comprehensive diagnostic workup and expands the clinical and molecular spectrum of MCL. Individualized low\u2212intensity targeted therapy may offer short\u2212term disease control in older patients with high\u2212risk MCL, though long\u2212term survival benefit remains unproven.\n                  <\/jats:p>","DOI":"10.3389\/fonc.2026.1878036","type":"journal-article","created":{"date-parts":[[2026,7,8]],"date-time":"2026-07-08T04:43:51Z","timestamp":1783485831000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Case Report: aleukemic mast cell leukemia with KIT p.V559G mutation, CD25-negative immunophenotype, and complex karyotype"],"prefix":"10.3389","volume":"16","author":[{"given":"Longyi","family":"Zhang","sequence":"first","affiliation":[{"name":"Clinical Laboratory, Affiliated Dongyang Hospital of Wenzhou Medical University","place":["Dongyang, Zhejiang, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lijing","family":"Jiang","sequence":"additional","affiliation":[{"name":"Department of Pathology, Affiliated Dongyang Hospital of Wenzhou Medical University","place":["Dongyang, Zhejiang, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xiaowei","family":"Zhang","sequence":"additional","affiliation":[{"name":"Department of Pathology, Affiliated Dongyang Hospital of Wenzhou Medical University","place":["Dongyang, Zhejiang, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yan","family":"Lu","sequence":"additional","affiliation":[{"name":"Clinical Laboratory, Affiliated Dongyang Hospital of Wenzhou Medical University","place":["Dongyang, Zhejiang, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xiaoxia","family":"Wang","sequence":"additional","affiliation":[{"name":"Department of Hematology, Affiliated Dongyang Hospital of Wenzhou Medical 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