Serpin A9?also known as?centerin?or?GCET1?is a?protein?that in humans is encoded by the?SERPINA9?gene?located on?chromosome?14q32.1.[1]?Serpin A9 is a member of the?serpin?family of?serine?protease?inhibitors. The expression of SERPINA9 is restricted to germinal center B cells and lymphoid malignancies. SERPINA9 is likely to function in vivo in the germinal center as an efficient inhibitor of trypsin-like proteases. Highly expressed in normal germinal center (GC) B-cells and GC B-cell-derived malignancies.