2021年血液病理学会和欧洲血液病理学协会研讨会第2节收集了B细胞系肿瘤中的谱系不规范和转分化的示例，包括经过靶向治疗后。共提交了20个病例。在少量的子样本上，整个外显子测序和全基因组RNA表达分析是可用的。对于至少13名患者的1个活检诊断为B细胞急性淋巴细胞白血病（B-ALL）。有1例急性髓性白血病（AML），其余6例为成熟的B细胞肿瘤。靶向治疗在7例B-ALL和4例成熟B细胞肿瘤中进行。6例B-ALL在复发时发生了谱系转换为AML或混合表型急性白血病，其中有5例重排了KMT2A。还观察到2例成熟B细胞淋巴瘤中出现了新的异常T细胞抗原表达，它们的存在与肿瘤细胞基因表达模式的改变相关。这些案例的队列使我们能够阐述，讨论和复习当前各种B细胞肿瘤中的谱系转换和异常抗原表达的概念，并引起我们对靶向治疗在使肿瘤易于发生转分化以及其他不太预期的成熟状况变化方面的作用的关注。©作者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。有关权限，请发送电子邮件至：journals.permissions@oup.com。

Session 2 of the 2021 Society for Hematopathology and European Association for Haematopathology Workshop collected examples of lineage infidelity and transdifferentiation in B-lineage neoplasms, including after targeted therapy.Twenty cases were submitted. Whole-exome sequencing and genome-wide RNA expression analysis were available on a limited subsample.A diagnosis of B-cell acute lymphoblastic leukemia (B-ALL) was rendered on at least 1 biopsy from 13 patients. There was 1 case of acute myeloid leukemia (AML); the remaining 6 cases were mature B-cell neoplasms. Targeted therapy was administered in 7 cases of B-ALL and 4 cases of mature B-cell neoplasms. Six cases of B-ALL underwent lineage switch to AML or mixed-phenotype acute leukemia at relapse, 5 of which had rearranged KMT2A. Changes in maturational state without lineage switch were observed in 2 cases. Examples of de novo aberrant T-cell antigen expression (n = 2) were seen among the mature B-cell lymphoma cohort, and their presence correlated with alterations in tumor cell gene expression patterns.This cohort of cases enabled us to illustrate, discuss, and review current concepts of lineage switch and aberrant antigen expression in a variety of B-cell neoplasms and draw attention to the role targeted therapies may have in predisposing neoplasms to transdifferentiation as well as other, less expected changes in maturational status.© 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.