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[Clinicopathological features of myeloid sarcoma and DLBCL in the breast: a comparative study].

Objective: 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.