摘要目的:探讨乳腺髓系肉瘤的临床病理学特征、诊断及鉴别诊断。方法:收集2005年2月至2019年9月北京大学人民医院病理科诊断的10例乳腺髓系肉瘤病历资料，与同期19例乳腺弥漫性大B细胞淋巴瘤（DLBCL）相对比，按2008版WHO淋巴造血组织肿瘤分类和2017版分类更新，应用光镜观察、免疫组织化学染色方法进行临床病理学分析。结果:10例髓系肉瘤患者均为女性，年龄范围23~47岁，平均年龄33.8岁。患者均表现为乳腺肿物。6例（6/10）有B症状。4例血清乳酸脱氢酶升高。肿物最大径1.0~5.3 cm,平均2.7 cm。10例均有急性髓性白血病（acute myeloid leukaemia,AML）病史，1例5年前因葡萄胎化疗后出现AML。其中M0 1例，M2 4例，M4 2例，M5 3例。10例患者均行化疗，9例行异基因造血干细胞移植，4个月至2年后出现乳腺肿物。Ann Arbor分期5例为Ⅰ期，3例为Ⅱ期，2例为Ⅳ期。病变位于乳腺左侧2例，右侧3例，双侧5例。2例除了乳腺病变以外，还伴有中枢神经系统、眼眶周围侵犯。与DLBCL病例比较，外周血淋巴细胞百分比、B症状、乳腺发病部位在髓系肉瘤与DLBCL之间差异具有统计学意义（均 P<0.05）。乳腺组织中可见弥漫增生的淋巴样细胞，排列呈巢状或条索状，细胞呈髓母细胞、髓单核或单核母细胞样。免疫组织化学表达髓过氧化物酶、CD43、CD117、CD34等，Ki-67阳性指数为30%~90%。治疗方法为手术切除，辅以化疗、放疗、供者淋巴细胞输注。10例随访时间1~50个月（平均14.4个月）,7例死亡。并发症有移植物抗宿主病、肺部感染、中枢神经系统白血病等。髓系肉瘤患者的总体生存情况比DLBCL差（ P=0.002）。 结论:乳腺髓系肉瘤少见，极少数病例可发生于骨髓移植后。临床病史、病理形态和免疫组织化学对于诊断具有重要作用。

abstractsObjective:To study the clinicopathological features, diagnosis and differential diagnosis of myeloid sarcoma of the breast.Methods:Ten cases of myeloid sarcoma (MS) and 19 cases of diffuse large B cell lymphoma (DLBCL) of the breast were selected from Peking University People′s Hospital from February 2005 to September 2019. The cases were evaluated by microscopy and immunohistochemistry basing on WHO classification (2008 and 2017).Results:For the 10 cases of MS, the mean and median age was 33.8 and 31 years (range 23 to 47 years) respectively. All patients presented with breast masses; six presented with B symptoms (6/10); and LDH level was elevated in four patients. The largest tumor dimension was 1.0 to 5.3 cm (mean 2.7 cm). All 10 patients had history of acute myeloid leukemia (AML), and in one patient, the AML occurred after chemotherapy for hydatidiform mole. One case was classified as M0, four were M2, two were M4 and three were M5. For the AML, all patients received chemotherapy and nine were treated by allogeneic hematopoietic stem cell transplant (allo-HSCT) and the breast masses occurred4 months to 2 years post-transplant. Using Ann Arbor staging, five cases were stage Ⅰ, three were stage Ⅱ, and 2 were stage Ⅳ. The MS was found in the left breast (two cases); right breast (three cases) and both breasts (five cases). Lymphocyte in peripheral blood, B symptom and site of lesion had statistical significance between myeloid sarcoma and DLBCL( P<0.05). The tumor cells were primitive, expressing MPO, CD43, CD117, etc. All ten patients had follow-up information, and the median survival period was 14.4 months (range 1 to 50 months). Seven patients died. The prognosis of patients with MS was worse than DLBCL( P=0.002). Conclusions:The clinical history, pathologic morphology, immunophenotyping and molecular studies are very important for diagnosing MS tumors in the breast, and MS may occur after allo-HSCT for AML. Tumor resection, chemotherapy, radiotherapy and donor lymphocyte infusion are recommended for treatment. The prognosis is poor.