PREFERENTIAL DISSEMINATION OF B-CELL GASTRIC MUCOSA-ASSOCIATED LYMPHOID-TISSUE (MALT) LYMPHOMA TO THE SPLENIC MARGINAL ZONE

The tendency for gastric mucosa-associated lymphoid tissue (MALT) lymp homa cells preferentially to localize around reactive B-cell follicles , both in the mucosa and regional lymph nodes, coupled with their immu nophenotype, has led to the proposal that the normal cell counterpart of this lymphoma is the marginal zone B cell. In keeping with this pro position, lymphocytes expressing the lymphoma idiotype have been detec ted in the splenic marginal zone in a single case of gastric MALT lymp homa. To confirm that this truly represented preferential homing of MA LT lymphoma to the splenic marginal zone, we have now re-examined this case, together with 17 other cases, using both immunohistochemical an d molecular methods in an attempt to establish clonal identity between the gastric lymphoma and cells in the splenic marginal zone. In three cases, the spleen was characterized by marked expansion of marginal z ones by cells showing the same pattern of lg light chain restriction a s the gastric lymphoma. None of the remaining 15 cases showed histolog ic evidence of lymphomatous infiltration. Analysis of the lg genes by polymerase chain reaction (PCR), cloning, and sequencing confirmed clo nal identity between the splenic marginal zone infiltrates and the gas tric lymphoma in the histologically involved cases. Amplifiable DNA co uld be extracted from only 5 of the remaining 15 cases. In 3 of these cases, including the case previously studied using an anti-idiotype, i nvolvement of the splenic marginal zone could be confirmed using micro dissection and clone-specific PCR. No involvement could be detected in the remaining 2 cases. In addition, we have shown that mucosal addres sin cell adhesion molecule-1 (MAdCAM-1), the primary homing receptor o f gut-mucosa for lymphocytes, was strongly expressed by the sinus lini ng cells of the splenic marginal zone. These results provide strong ev idence for preferential involvement of the marginal zone when gastric MALT lymphomas disseminate to the spleen, which is in keeping with the notion that the marginal zone B cells are the normal counterparts of MALT lymphoma cells. (C) 1997 by The American Society of Hematology.