A PCR ANALYSIS OF BCL-2 GENE REARRANGEMENT IN NODAL AND EXTRANODAL NON-HODGKINS-LYMPHOMA (NHL) - SOME UNUSUAL OBSERVATIONS IN SAUDI PATIENTS

Non-Hodgkin's lymphoma (NHL) is the most common malignancy referred to our institute which is the largest tertiary referral cancer centre in Saudi Arabia, The proportion of follicular low grade NHL appears to b e extremely small in this population (<5% of all NHL). To date, there is no data available regarding any correlation between bcl-2 gene rear rangement and different cell types of nodal and extranodal NHLs in Sau di patients. We used a sequential polymerase chain reaction (PCR) tech nique to determine the frequency of bcl-2/J(H) recombination occurring via the major breakpoint region (mbr) in 16 GI tract NHLs including 4 MALT lymphomas and 13 follicular (nodal) NHLs. The results showed onl y 2/13 (15%) nodal follicular NHLs with bcl-2/J(H) fusion DNA whereas 9/16 (56%) of the extranodal NHLs with at least 2 of them exhibiting M ALT characteristics were positive for the bcl-2 gene rearrangement. A breakdown of the proportion of extranodal NHLs of different cell types showing bcl-2 rearrangement via mbr was as follows: 5/8 diffuse large non-cleaved cell (DLNCC), 1/3 diffuse small cleaved cell (DSCC), 1/1 follicular small cleaved cell (FSCC) and 2/4 MALTs. The PCR amplified bcl-2/J(H) fusion DNA from 5 randomly selected tumors (2 MALTs, 1 DLNC C, 1 DSCC and 1 nodal follicular lymphoma) were cloned and sequenced. All 5 of them showed different bcl-2/J(H) N-regions confirming the clo nality of each tumor sample. The data indicating a very low incidence of bcl-2 translocation in nodal follicular NHLs and a surprisingly hig h incidence of it in extranodal NHLs are intriguing, and quite contrar y to the findings in Western patients. These unusual observations warr ant further studies and may suggest that different genetic events are involved in the development of extranodal NHLs including MALT and foll icular center-cell NHLs in Saudi patients.