Centerin (SERPINA9/GCET1) is a protease inhibitor with expression restricted to germinal center B cells and lymphoid malignancies with germinal center B-cell maturation. Expression of the centerin gene transcript, along with bcl-6 and GCET2/HGAL, constitutes a molecular signature associated with a good prognosis in diffuse large B-cell lymphomas. A monoclonal antibody to centerin was generated and used for Western blotting, immunohistochemistry, and immunofluorescence. Centerin expression was demonstrated in Burkitt lymphoma Raji cells. An immunohistochemical survey of normal tissues showed centerin expression in germinal center B cells in lymphoid follicles in tonsil, lymph node, and lymphoid tissue in the gastrointestinal tract. Centerin was strongly expressed in most follicular lymphomas. In addition, 14 (47%) of 30 diffuse large B-cell lymphomas were positive for centerin, which correlated most closely with CD10 expression. Immunohistochemical expression of centerin further defines the germinal center cell origin of a subgroup of lymphomas.