摘要目的:探讨未定类树突细胞肿瘤（indeterminate dendritic cell tumor，IDCT）的临床病理、免疫组织化学及分子病理特征。方法:对北京协和医院（3例）和福建省立医院（1例）2015年1月至2019年7月收集的4例IDCT进行组织形态学、免疫组织化学染色、BRAF V600E基因检测，并随访及复习相关文献进行综合分析。结果:男性2例，女性2例，发病年龄30~52岁（平均年龄40岁）。病理组织学特征，瘤细胞呈圆形、多角形，细胞核圆形，胞质丰富嗜酸性，瘤细胞呈片状、旋涡状，束状排列。瘤细胞可见核仁，核分裂象（1~3）个/10 HPF，间质可见淋巴细胞、浆细胞等浸润。免疫表型：瘤细胞呈S-100蛋白（4/4）、CD1a（4/4）、CD68（4/4）、cyclin D1（3/3）阳性，Ki-67阳性指数5%~30%，CD207/Langerin、Ki-67、广谱细胞角蛋白（CKpan）、CD21、HMB45、间变性淋巴瘤激酶（ALK）、肌动蛋白阴性。分子病理检测，4例均未见BRAF V600E基因突变。结论:IDCT属于罕见的树突细胞肿瘤，形态学无特异性表现，诊断依赖于临床病理及免疫表型，必要时行电镜检查及分子病理学检测。

abstractsObjective:To investigate the clinicopathologic features, diagnosis, differential diagnosis and molecular pathological characteristics of indeterminate dendritic cell tumor (IDCT).Methods:Four cases of IDCT were collected at Peking Union Medical College Hospital (3 cases) and Fujian Provincial Hospital (1 case). The 4 cases were analyzed, with focus on morphology, immunohistochemistry and BRAF V600E detection. Related literature was reviewed to reveal the characteristics of this tumor.Results:There were 2 males and 2 females aged 30-52 years (mean=40 years). Histopathological characteristics of the tumor cells were round, polygonal. The nuclei were round, with rich eosinophils cytoplasm. The tumor cells arranged in diffuse, sheet, whorl, and fascicle patterns. Mitosis was variable [generally(1-3)/10 HPF] and nucleoli were obvious. Lymphocytes, plasma cells and other infiltrates could be seen in the stroma. Immunohistochemically, tumor cells were positive for S-100 (4/4), CD1a (4/4), CD68 (4/4) and cyclin D1 (3/3), while CD207/Langerin, CKpan, CD21, HMB45, ALK and actin were negative. Ki-67 index was 5%-30%. Gene detection showed BRAF V600E mutations were not present in any of the four cases.Conclusions:IDCT is a rare type of dendritic cell tumor. There are no specific morphology characteristics. The diagnosis depends on clinical, histopathological and immunophenotype. Thus, electron microscopy and molecular testing are helpful if necessary.