报告2021年血液病理协会/欧洲血液病理协会研讨会在B细胞系肿瘤向组织细胞/树突细胞肿瘤(HDCNs)的转分化类别中的发现。研讨会小组评估了29例病例，分配了共识诊断并总结了发现。转分化HDCN肿瘤的具体诊断为组织细胞瘤(16例)、朗格汉斯细胞性肥大细胞组织细胞瘤/肉瘤(5例)、不确定的DC肿瘤(1例)和未分类的HDCN(1例)。大约三分之一的病人被审查为滤泡性淋巴瘤；淋巴母细胞白血病/淋巴瘤；或其他B细胞淋巴瘤，最常见的是慢性淋巴细胞白血病/小淋巴细胞性淋巴瘤。女性占3:1，中位患者年龄为60岁，B细胞系肿瘤和HDCN之间的中位间隔年数为4到5年。提交的案例展示了显著的异质性以及重叠的免疫表型和其他特征。全面的基因组DNA测序显示富集在MAPK通路中的改变。基于HDCN和前面的淋巴瘤中看到的共同和独特的变化，推断了线性和分支的克隆演化途径。此外，在一部分案例中进行的RNA测序揭示了可能对更精确的细胞系谱鉴定有用的标记。因此，小组提出了更新的HDCN谱系分配算法。转分化HDCN的结果不佳，但MAPK信号通路成为一个潜在的有吸引力的治疗靶点。转分化HDCN表现出异质性并对确切分类提出诊断挑战，但提交的案例的深入表征增加了我们对由B细胞淋巴瘤/白血病转分化的HDCN的二次理解。持续努力关注这些肿瘤的特定细胞系和分化状态的揭示对于准确的分类至关重要。HDCN的全面分子特征描述可能在这方面是信息的。随着MAPK通路的新药物抑制剂列表不断扩大，HDCN的改善治疗效果可以预期。©作者(s)2023年。由牛津大学出版社代表美国临床病理学会出版。保留所有权利。请发送电子邮件至journals.permissions@oup.com获取许可。

To report findings from the 2021 Society for Hematopathology/European Association for Haematopathology Workshop within the category of B-cell lineage neoplasms' transdifferentiation into histiocytic/dendritic cell neoplasms (HDCNs).The workshop panel reviewed 29 cases, assigned consensus diagnoses, and summarized findings.The specific diagnoses of transdifferentiated HDCN tumors were histiocytic sarcoma (16); Langerhans cell histiocytosis/sarcoma (5); indeterminate DC tumor (1); and HDCN, unclassifiable (1). Approximately one-third of the patients reviewed had follicular lymphoma; lymphoblastic leukemia/lymphoma; or another B-cell lymphoma, most commonly chronic lymphocytic leukemia/small lymphocytic lymphoma. There was a 3:1 preponderance toward women, median patient age was 60 years, and the median interval between the initial diagnosis of B-cell lineage neoplasm and HDCN was 4 to 5 years. The submitted cases have demonstrated substantial heterogeneity as well as overlapping immunophenotypic and other features. Comprehensive genomic DNA sequencing revealed alterations enriched in the MAPK pathway. Based on shared and distinct alterations seen in HDCNs and the preceding lymphomas, both linear and divergent clonal evolutionary pathways were inferred. Furthermore, RNA sequencing performed in a subset of cases yielded new insights into markers that could be useful for more precise cell lineage identification. The panel has thus proposed an updated algorithm for HDCN lineage assignment. The outcome of transdifferentiated HDCNs was poor, but the MAPK signaling pathway emerges as a potentially attractive therapeutic target.Transdifferentiated HDCNs demonstrate heterogeneity and pose diagnostic challenges with regard to exact classification, but the in-depth characterization of the submitted cases have added to our understanding of the secondary HDCNs transdifferentiated from B-cell lymphoma/leukemia. Continuous efforts focusing on deciphering the specific cell lineage and differentiation state of these tumors will be critical for their accurate classification. Comprehensive molecular characterization of HDCNs may be informative in this regard. With the list of novel pharmacologic inhibitors of the MAPK pathway continuing to expand, improved outcomes for HDCN can be expected.© The Author(s) 2023. Published by Oxford University Press on behalf of American Society for Clinical Pathology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.