Primary breast lymphomas are uncommon. All reported primary breast lymphomas were in the breast parenchyma. Here we reported the first case of primary nipple lymphoma in a 76-year-old woman initially diagnosed using a modified fine-needle aspiration method. The aspirated material by this method had yielded adequate material for both cytomorphologic and flowcytometric analysis, as well as for molecular analysis of light chain rearrangement. In smears the atypical lymphocytes were predominantly middle-sized with irregular nuclei. Scattered large centroblast or immunoblast-like cells, a few reactive lymphocytes,histocytes, and few plasma cells were also observed. These findings suggested a low-grade lymphoma that was further confirmed by flow cytometry (CD19+/CD3-, positive for cytoplasmic kappa light chain but negative for lambda light chain) and molecular analysis (monoclonal rearrangement of immunoglobulin kappa chain). Immunohistochemical stains performed on the excised specimen showed that the tumor cells were positive forCD20 and CD79a but negative for cytokeratin, CD3, CD5,CD10, CD23, CD43, CD45RO, bcl-6, and cyclin-D1. The Ki-67 proliferation index was less than 20%. Taking these together, the case was diagnosed as a primary MALT lymphoma of the nipple.FNA usually provides a better cell morphology than tissue sections, but pathologists have to face the sampling error and lack of immunophenotype information when subtyping lymphoma issues using FNA. With the help of flow cytometry and molecular analysis, more and more trials have proved the accuracy of FNA in diagnosis of lymphomas. Therefore, FNA could play an informative and diagnostic role in diagnosis of lymphoma
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