<prompt> All are true about follicular lymphoma except:CD 20CD 5Bc1-1 positive in follicular lumphoma where as Bel-2 positive in mantle cell lymphomaTranslocation of 14:18  <response>: Ans. is b i.e.CD 5 Follicular lymphoma o Follicular lymphoma is the most common form of indolent non-Hodgkins lymphomas and the second most common form of non-Hodgkins lymphoma overall. o It is the tumor of germinal center follicular center, B cells, and is strongly associated with chromosomal translocation involving Bcl 2 o Growth pattern is nodular follicular or nodular follicular and diffuse. o Two principal cell types are present in varying propoion: i Small cleared cells centrocytes ii Centroblasts o In most follicular lymphomas, centrocytes predominate. Immunophenotype The neoplastic cells closely resemble normal germinal center B cells, expressing CD19, CD 20, CD 10, surface Ig, and Bel 6. o Unlike CLLSLL and mantel cell lymphoma, CD 5 is not expressed. o Bcl 2 is expressed in more than 90 of cases, in distinction to normal follicular center B cells, which are Bcl 2 negative, and mantel cell lymphoma cells which express BCL 1 cyclin D1. Molecular pathogenesis o The hallmark of follicular lymphoma is 14:18 translocation that juxtaposes the IgH locus on chromosome 14 and the Bel 2 locus on chromosome 18. Bcl 2 antagonizes the apoptosis and promotes the survival of follicular lymphoma cells -- while normal germinal centers contain numerous B cells undergoing apoptosis, follicular lymphoma is characteristically devoid of apoptotic cells 