Primary breast diffuse large B-cell lymphoma shows an activated B-cell-like phenotype.

Patients with diffuse large B-cell lymphoma (DLBCL) can be divided into germinal center B-cell-like subtype (GCB-DLBCL) and activated B-cell-like type (ie non-GCB-DLBCL) and with a prognostic value based on the cell of origin of the tumor as determined by microarray analysis, as well as by immunostain algorithms. To stratify primary breast DLBCL, according to immunostain algorithms of Hans, Choi, and Meyer (Tally), the reason why primary breast DLBCL possesses a poor clinical outcome was further elucidated. Twenty-two cases of primary breast DLBCL, diagnosed according to the 2008 World Health Organization classification of tumors of hematopoietic and lymphoid tissues, were retrospectively studied. Immunochemical study was performed, and follow-up information was analyzed. The histopathologic and immunophenotypic features of all cases were summarized. Among these 22 cases, most (17, 16, and 17, respectively) were assigned to the activated B-cell-like subtypes, few (5, 6, and 5, respectively) were classified as GCB-DLBCL subtype. Fourteen of these 22 cases expressed high proliferative activity (≥40% Ki-67 labeling). Most primary breast DLBCLs have activated B-cell-like subtype characteristics and high proliferative activity; these features might be a significant factor.