摘要目的:探讨婴儿纤维性错构瘤（fibrous hamartoma of infancy，FHI）的临床病理学特征、免疫表型、分子遗传学特点。方法:收集河南省人民医院病理科2011年10月至2020年12月经手术切除的的33例FHI患者的临床及病理学资料，结合随访资料进行分析，并应用二代测序技术及即时荧光定量聚合酶链反应（q-PCR）技术对其进行分子遗传学研究。结果:本组患者发病年龄范围6个月至6岁，平均16.7个月，男患儿21例，女患儿12例，发病部位包括躯干（21例）、四肢（11例）、颈部（1例）。均表现为无痛性孤立性浅表软组织肿块，大小为1.5~9.0 cm（平均3.8 cm）。镜下均由成熟脂肪组织、纤维母细胞/肌纤维母细胞束及原始间叶细胞以不同比例混合组成，14例中见多少不等的巨细胞纤维母细胞瘤样区域。免疫组织化学示梭形细胞和原始间叶成分不同程度表达表皮生长因子受体（EGFR），多数病例中梭形细胞表达CD34和平滑肌肌动蛋白，伴巨细胞纤维母细胞瘤样区域均强表达CD34，脂肪细胞恒定表达S-100蛋白，Ki-67阳性指数1%~5%。6例行二代测序检测均存在体细胞EGFR第20号外显子插入/重复突变，共检出3种不同的突变类型：p.Asn771_His773dupAsnProHis、p.Pro772_His773insProProHis和p.His773_Val774insThrHis。应用q-PCR方法对该6例及另外15例FHI进行验证，均显示有EGFR第20号外显子插入/重复突变。结论:FHI是一种少见的良性纤维母细胞/肌纤维母细胞性肿瘤，器官样三相性形态是其特征性的组织学特点，体细胞EGFR第20号外显子插入/重复突变是其分子特征。

abstractsObjective:To investigate the clinicopathological features, immunophenotypic and molecular genetic characteristics and differential diagnosis of fibrous hamartoma of infancy (FHI).Methods:Thirty-three cases of surgically removed FHI were collected from the Department of Pathology, Henan Provincial People′s Hospital from October 2011 to December 2020, the clinical and pathologic data with follow-up were collected and analyzed. Next-generation sequencing (NGS) and quantitative real time polymerase chain reaction (q-PCR) were used to study the molecular genetics.Results:The FHI cases occurred in 21 males and 12 females (mean age 16.7 months, range 6 months to 6 years). The sites included trunk ( n=21), limb ( n=11), and neck (n=1). All patients had painless solitary superficial soft tissue masses, the size was 1.5-9.0 cm (mean 3.8 cm). Microscopically, they were composed of mature adipose tissue, fibroblast/myofibroblast bundle and primitive mesenchymal cells in different proportions; giant cell fibroblastoma-like areas were seen in 14 cases. Immunohistochemistry showed variable expression of EGFR in the spindle cells and primitive mesenchymal components. In most cases, the spindle cells were positive for CD34 and SMA; giant cell fibroblastoma-like areas were strongly positive for CD34; and S-100 protein was expressed by adipocytes in all cases. Ki-67 labeling index ranged 1%-5%. There were recurrent somatic EGFR exon 20 insertion/duplication mutations in six cases tested by NGS, and there were three different mutation types: p.Asn771_His773dupAsnProHis, p.Pro772_His773insProProHis, and p.His773_Val774insThrHis. All the above 6 and another 15 tested cases showed EGFR exon 20 insertion/duplication mutations by q-PCR. Conclusions:FHI is a rare benign fibroblast/myofibroblast tumor. The characteristic histologic feature is organoid triphasic morphology, and the molecular feature is somatic mutation of EGFR exon 20 (insertion/duplication).