Abilateral adnexectomy and retroperitoneal lymph node biopsy were performed.Lined with squamous epithelium, the cyst constituted a mature ovarian teratoma,and the solid part showed diffuse proliferation of abnormal lymphoid cells.Immunohistochemically, the abnormallymphoid cells were negative for CD5, MUM1, and CyclinD1, and positivefor CD10, CD20, CD21, BCL2, and BCL6. The gene discussed is BCL6; the disease is ovarian teratoma.