Expression of LAZ3/BCL6 in follicular center (FC) B cells of reactive lymph nodes and FC-derived non-Hodgkin lymphomas. 
Chromosomal translocation resulting in abnormal expression of the LAZ3/BCL6 gene in B cells has been implicated in the tumorigenesis of non-Hodgkin lymphoma (NHL).  Therefore we studied the expression pattern of LAZ3/BCL6 by in situ hybridization with synthetic oligonucleotide probes in frozen tissue sections from five reactive lymph nodes and 38 B cell and non-B NHL.  In addition, we investigated the expression of LAZ3/BCL6 by Northern blot analysis on multiple human tissues.  The LAZ3/BCL6 transcript was found in a variety of tissues, including skeletal muscle, peripheral blood leukocytes, and weakly in normal lymph nodes.  In the tumor samples, expression of LAZ3/BCL6 was observed in 68% of all B cell NHL and none of the non-B lymphomas.  All cases of follicular, mixed small and large cell lymphomas showed LAZ3/BCL6 expression confined to the neoplastic follicles.  A follicular expression pattern was also found in all non-malignant reactive lymph nodes.  Hence, the expression of LAZ3/BCL6 does not correlate to malignancy, but reflects the origin of B cells from the germinal centers.