BCL-6 (B-Cell CLL/Lymphoma 6, zinc finger protein 51) is a 95 kDa zinc-finger transcription factor. It is required for germinal centre formation and is involved in the differentiation of normal germinal centre B-cells. BCL-6 acts a sequence-specific repressor of transcription and is a suppressor of p53 expression (Phan and Dalla-Favera). As an immunohistochemical marker, BCL-6 is used alongside a panel of other lymphoma markers to determine lymphomas of B-cell origin: it is most commonly detected in germinal centre neoplasms such as follicular lymphoma, diffuse large B-cell lymphoma, Burkitt’s lymphoma and lymphocyte predominant Hodgkin’s lymphoma (Cattoretti et al., Skinnider et al., Wlodarska et al., Raible et al.) BCL-6 expression is absent in acute lymphatic leukaemia and mantle cell lymphoma.