OBJECTIVETo investigate the clinicopathologic and immunophenotypic features of primary breast lymphoma (PBL) and to discuss the diagnosis of the tumor.

METHODSTwenty-one cases of PBL with follow up data were clinically reviewed. The histologic diagnosis of the tumor was based on the updated WHO Classification of tumors of hematopoietic and lymphoid tissues (2008). Immunohistochemistry was performed by SP method and antibodies selected were as follows: CD20, CD3epsilon, CD10, Bcl-6, MUM-1, CD5, Bcl-2, CD23, CD10, cyclin D1, CD43 and Ki67.

RESULTS(1) All 21 patients were female and the median age of patients was 48 years. The right and the left breasts were involved in 11 (52.4%) and 10 patients (47.6%), respectively. According to Ann Arbor staging system, 20 cases were stage I-II (95.2%), and the remaining case was stage IV (4.8%). For the international prognostic index (IPI), 19 cases were score 0-1, and 2 cases were score 2-3. For ECOG score, 19 cases were 0, and the remaining 2 cases were 1. (2) Histologically, all 21 cases (100%) were DLBCL. Immunohistochemically, the frequency of antigen expression was as follows: CD20 (100%), MUM-1 (14/21, 66.7%), bcl-6 (5/21, 23.8%), CD10 (0), bcl-2 (13/21, 61.9%), CD5 (1/21, 4.8%); Ki-67 index: 10 cases (47.6%) were less than 59%, with the expression of seven cases (33.3%) being 60% - 89%, and more than 90% in the remaining four cases (19.1%). The median Ki-67 index was 60%. All the cases were considered non germinal center B-cell-like type of DLBCL. (3) Follow-up data was available in 64% of the cases. One, two and five-year survival rates were 11 cases, 7 cases and 3 cases, respectively.

CONCLUSIONAll the cases of PBL in the current study were DLBCL, non germinal center B-cell-like type, and a diagnosis of PBL can only be established after excluding breast involvement in systemic lymphoma.