目的 探讨儿童弥漫性中线胶质瘤伴H3 K27改变的临床病理特征。方法 回顾性分析2016年9月至2021年7月首次诊断为弥漫性中线胶质瘤伴H3 K27改变患儿的临床和病理资料。结果 共纳入95例患儿，男54例、女41例，中位年龄6.0（5.0~9.0）岁；脑干为好发部位（82.1%）。肿瘤WHO组织学分级1~4级皆有分布，以高级别胶质瘤为多数（65.3%）。免疫组织化学检测显示所有病例的H3 K27M（组蛋白H3第27位赖氨酸改变为甲硫氨酸）均为阳性表达，89.0%患儿的H3 K27Me3（组蛋白H3第27位赖氨酸的三甲基化）表达下降。55.6%患儿表达突变型肿瘤蛋白53（P53）；异柠檬酸脱氢酶1（IDH1）表达率和α地中海贫血/智力低下综合征X 连锁（ATRX）表达缺失率均低，分别为8.5%和18.6%；而鼠类肉瘤滤过性病毒致癌同源体B1（BRAF）仅有1例表达（1.2%）。47.1%（8/17）患儿出现O-6-甲基鸟嘌呤-DNA甲基转移酶（MGMT）基因甲基化阳性。2.1%（1/48）患儿发生BRAF基因变异。结论 弥漫性中线胶质瘤伴H3 K27改变患儿的好发部位为脑干，组织学分级以高级别为多数，ATRX蛋白缺失率较低，且与肿瘤发生部位无关。

Objective To investigate the clinicopathological characteristics of pediatric H3 K27-altered diffuse midline gliomas (DMG). Methods The clinical and pathological data of children first diagnosed with H3 K27-altered DMG from September 2016 to July 2021 were retrospectively analyzed. Results A total of 95 patients (54 boys and 41 girls) were included, and the median age was 6.0 (5.0-9.0) years. Brainstem was the predilection site (82.1%). WHO histological grade 1-4 tumors were found in all cases and high-grade gliomas were found in most cases (65.3%). Immunohistochemical detection showed that H3 K27M (the 27th lysine of histone H3 changed to methionine) was positively expressed in all cases, and H3 K27Me3 (the trimethylation of the 27th lysine of histone H3) was decreased in 89.0% of the children. Mutant p53 (P53) was expressed in 55.6% of the children. The expression rate of isocitrate dehydrogenase 1 (IDH1) and loss expression rate of alpha-thalassemia/mental retardation syndrome X-linked (ATRX) were low (8.5% and 18.6%, respectively). V-Raf murine sarcoma viral oncogene homolog B1 (BRAF) was positive in only 1 case (1.2%). Molecular tests showed that O-6-methylguanine-DNA methyltransferase (MGMT) methylation was detected in 8 cases (47.1%, 8/17), and BRAF variation was detected in 1 case (2.1%, 1/48). Conclusions The commonest location of H3 K27-altered DMG children is the brainstem, and the histological grade is mostly high. ATRX loss in pediatric cases is less common and had no relationship with the tumor location.