母细胞性浆细胞样树突状细胞肿瘤（BPDCN）是一种罕见的侵袭性血液肿瘤，其临床、形态学和免疫表型与急性髓系白血病有重叠。骨髓细胞核分化抗原 (MNDA) 是一种由骨髓单核细胞表达的核蛋白，之前报道在 BPDCN 中确实不存在，并建议作为区分 BPDCN 和急性髓系白血病的有用辅助剂。我们遇到了一例 BPDCN 病例，其在骨髓和乳腺样本中显示 MNDA 的核强表达，而在皮肤样本中表达较弱甚至缺失，促使我们重新评估 BPDCN 中 MNDA 的表达。我们从斯坦福大学档案中收集了所有可用的 BPDCN 病例收集过去 10 年的数据并进行 MNDA 免疫组织化学分析。在选定的病例中，通过下一代测序进行了分子分析。我们发现 4 例（总共检查了 8 例 [50%]）具有令人信服的位点不一致 MNDA 表达。该表达见于 6 个骨髓样本中的 3 个（50%）、2 个乳房软组织样本中的 1 个（50%）以及 14 个皮肤样本中的 3 个（高达 21%），并且不能通过年龄、性别、骨髓肿瘤病史或治疗史。在 2 例病例中，MNDA 在 2 个不同部位（乳腺/骨髓、皮肤/骨髓）强烈表达，而在随后的样本中呈阴性。我们的研究结果表明，BPDCN 中的 MNDA 表达具有解剖部位依赖性和短暂性，非皮肤浸润更频繁表达高于皮肤浸润。这些结果提醒我们，在考虑髓外浸润的鉴别诊断时，不要使用 MNDA 来排除 BPDCN。© 作者 2024。由牛津大学出版社代表美国临床病理学会出版。版权所有。如需商业重复使用，请联系 reprints@oup.com 获取转载和转载的翻译权。所有其他权限都可以通过我们网站文章页面上的权限链接通过我们的 RightsLink 服务获得 - 如需更多信息，请联系journals.permissions@oup.com。

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive hematologic neoplasm that can show clinical, morphologic, and immunophenotypic overlap with acute myeloid leukemia. Myeloid cell nuclear differentiation antigen (MNDA) is a nuclear protein expressed by myelomonocytic cells previously reported to be reliably absent in BPDCN and proposed as a useful adjunct for the distinction of BPDCN and acute myeloid leukemia. We encountered a case of BPDCN that showed strong nuclear expression of MNDA in bone marrow and breast samples and weak to absent expression in skin samples, prompting us to reevaluate the expression of MNDA in BPDCN.We collected all available BPDCN cases from the Stanford University archives collected in the past 10 years and subjected them to MNDA immunohistochemistry. In select cases, molecular profiling by next-generation sequencing was performed.We found 4 cases (of 8 total examined [50%]) with convincing site-discordant MNDA expression. This expression was seen in 3 of 6 (50%) bone marrow samples, 1 of 2 (50%) breast soft tissue samples, and 3 of 14 (up to 21%) skin samples and was not obviously predicted by age, sex, history of myeloid neoplasm, or treatment history. In 2 cases, MNDA was strongly expressed in 2 distinct sites (breast/bone marrow, skin/bone marrow) and negative in subsequent samples.Our findings suggest that MNDA expression in BPDCN is anatomic site dependent and transient, with noncutaneous infiltrates showing more frequent expression than cutaneous infiltrates. These results caution against the use of MNDA to exclude BPDCN when considering the differential diagnosis of a blastic extramedullary infiltrate.© The Author(s) 2024. Published by Oxford University Press on behalf of American Society for Clinical Pathology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.