Lymphoma of the breast - A clinicopathologic study of primary and secondary cases

Background.--Primary lymphomas of the breast are rare, accounting for 1.7% to 2.2% of extranodal lymphomas and 0.38% to 0.7% of all non-Hodgkin lympho mas. Although secondary breast lymphomas are also rare, they represent the largest group of metastatic tumors of the breast. Objectives.--To investigate the clinicopathologic and immunophenotypic char acteristics of breast lymphomas, the relative frequency of primary and seco ndary mammary lymphomas, and in selected cases, the role of gene rearrangem ent analysis in diagnosis and staging of these lymphomas. Results.--We conducted a retrospective review of 22 cases of breast lymphom a diagnosed at William Beaumont Hospital, Royal Oak, Mich, during a 30-year period (1963-1994). Eleven of the 22 cases fulfilled the criteria for prim ary breast lymphoma; these cases represented 0.6% of all non-Hodgkin lympho mas seen in our hospital. Of the 11 cases, 5 were diffuse large B-cell lymp homas, 2 were follicle center lymphomas, 2 were marginal zone B-cell lympho mas (mucosa-associated lymphoid tissue type), 1 was a lymphoplasmacytoid ly mphoma, and 1 was a peripheral B-cell neoplasm, unclassified. Using a panel of immunohistochemical stains (CD45RO, CD45RA, CD43, CD3, CD20, CD30, CD68 , and HLA-DR), 8 cases demonstrated unequivocal B-cell phenotype and 3 case s had equivocal or weak staining patterns for B-cell markers. We identified no cases of T-cell lymphoma. Of 7 cases that had bone marrow biopsies for staging, 3 were positive morphologically for bone marrow involvement. Molec ular analysis of B- and T-cell gene rearrangement was used to exclude bone marrow involvement in one case with bone marrow lymphoid aggregates and to confirm negativity in a case that was morphologically negative. Of the 11 s econdary breast lymphomas, 5 were diffuse large B-cell lymphomas; 1 was dif fuse large B-cell, primary mediastinal subtype; and 5 were follicle center lymphomas. Conclusions.--Breast lymphomas represented 1.2% of all non-Hodgkin lymphoma s in this study; the frequency of primary and secondary cases was equal. In both groups, right breast lesions were predominant, and the most frequent morphologic type was diffuse large B-cell lymphoma. Gene rearrangement anal ysis is helpful in selected cases to rule out bone marrow involvement, espe cially in older patients, in whom lymphoid aggregates are common.