[Langerhans cell histiocytosis in children: clinicopathological and ultrastructural analyses of 345 cases].

Objective: To investigate the clinicopathological and ultrastructural characteristics of Langerhans cell histiocytosis (LCH) in children. Methods: A total of 345 cases of LCH from the Department of Pathology, Beijing Children Hospital from January 2012 to March 2016 were investigated by hematoxylin-eosin stain, EnVision immunohistochemistry and transmission electron microscopy. Results: The rate of primary clinical diagnosis of LCH in children was 46.0%(210/457). Among 345 patients of LCH, 213 were male and 132 were female, the male to female ratio was 1.6∶1.0, and the median age was 21 months (range from 2 days after birth to 13.3 years). There were total 597 lesions, including bony lesions (258, 43.2%), skin lesions (206, 34.5%) , followed by lymph node (16, 2.7%), lung (28, 4.7%), liver (25, 4.2%) and head-neck (50, 8.4%). Single organ system LCH (SS-LCH) was seen in 295 cases (85.5%) and 50 cases (14.5%) presented with multiple organ system involvement LCH (MS-LCH). There was no significant difference in age and gender between SS-LCH and MS-LCH groups. Regarding sites, more lesions were seen in bone and skin in SS-LCH group, in contrast lymph node, lung, liver and head-neck involvements were often seen in MS-LCH group. Immunohistochemically, the expression of CD1a and Langerin was seen in 99.7% (341/342) and 98.8% (338/342) of the cases respectively. The diagnostic rates by light and transmission electron microscopy were 98.8% (341/345) and 97.4% (112/115) respectively (P>0.05). Conclusions: LCH of children occurs predominantly in SS-LCH pattern, frequently involving bone, skin, lymph node, lung and liver and other sites with unique histopathological, immunophenotypical and ultrastructural features. Accurate diagnosis relies on the morphology, immunophenotype and ultrastructural features. Further refinement of specimen processing may improve the accuracy of pathological diagnosis.目的： 探讨儿童朗格汉斯细胞组织细胞增生症（Langerhans cell histiocytosis，LCH）的临床病理及超微结构特点。 方法： 收集首都医科大学附属北京儿童医院病理科2012年1月至2016年3月期间诊断的345例LCH，采用HE染色、免疫组织化学EnVision法及透射电镜技术进行研究。 结果： （1）儿童LCH的临床初诊符合率为46.0%（210/457）。（2）345例LCH中，男213例，女132例。男女比为1.6∶1.0，中位年龄1岁9个月（生后2 d至13岁4个月），共有发病部位597处，以骨258处（43.2%）、皮肤206处（34.5%）为主，其次淋巴结16处（2.7%）、肺28处（4.7%）、肝脾25处（4.2%）、头颈部（眼周、耳、口腔）50处（8.4%）等。单系统LCH 295例（85.5%），多系统LCH 50例（14.5%）。两种系统中，患儿的性别、发病年龄分组中的差异均无统计学意义（P>0.05）；而患儿各发病部位分组中的差异均有统计学意义（P<0.05），发生于骨、皮肤的病变多见于单系统组，而累及淋巴结、肺、肝、脾、头颈部（口腔、耳、眼周）及少见部位的病变在多系统中更多见。（3）CD1a及Langerin阳性表达率分别为99.7%（341/342）和98.8%（338/342）。光镜和透射电镜诊断符合率分别为98.8%（341/345）和97.4%（112/115），二者之间的差异无统计学意义（P>0.05）。光镜漏诊病例为皮肤及骨组织各2例，透射电镜漏诊的3例均为骨组织。 结论： LCH好发于婴幼儿，单系统病变多见，好发于骨、皮肤、淋巴结、肺、肝等部位，具有独特的组织病理、免疫表型和超微结构特点，确诊需依靠组织病理、免疫表型和/或超微结构特点综合考虑。.