Objective  To investigate the clinical characteristics, treatment regimens, and outcomes of patients with primary breast diffuse large B-cell lymphoma (PB-DLBCL).

  Methods  Between January 2010 and January 2018, 21 patients with PB-DLBCL were diagnosed, treated, and followed up at the First Affiliated Hospital of Zhengzhou University. All patients were female, with a median age of 49 years (ranging from 21 to 77 years) at presentation. All patients received chemotherapy, of which 17 patients received the CHOP regimen and 4 received the EPOCH regimen. Eight patients received chemotherapy followed by radiotherapy, and 13 received chemotherapy alone. Six patients received prophylactic intrathecal injections. The incidences of refractory and progressive disease between patients who received different regimens were analyzed using the Chi-square test. The overall survival (OS) and progression-free survival (PFS) rates were calculated using the Kaplan-Meier method, and differences in survival were compared using the Log-rank test. Multivariate analysis was performed with the Cox-regression model for those factors that were confirmed as significant in the univariate analysis.

  Results  The most common presentation was a painless mass. The 5-year OS and PFS rates were 74% and 66%, respectively. There was no significant difference in the incidence of refractory or progressive disease between the EPOCH and CHOP groups (P=0.603). Six of those who received prophylactic intrathecal injections had no central nervous system recurrence, and 2 patients who did not receive prophylactic intrathecal injections had central nervous system recurrence. Univariate and multivariate analyses showed that both the level of serum β2 microglobulin P=0.044, hazard ratio (HR)=0.431, 95% confidence interval (CI): 0.432-0.967 and radiotherapy (P=0.002, HR=0.495, 95% CI: 1.073-2.508) were related to the OS of PB-DLBCL.

  Conclusions  PB-DLBCL often occurs in women, mostly involving the unilateral breast, which manifests mainly as a painless mass. The level of serum β2 microglobulin is a factor of poor prognosis in PB-DLBCL. The treatment modality of chemotherapy combined with radiotherapy can significantly improve the OS of PB-DLBCL. Prophylactic intrathecal injections may be useful to reduce the incidence of refractory disease or recurrence in the central nervous system.