An Immunohistochemical Analysis of Gastric B-cell Lymphomas : Stromal Cells Exhibit Peculiar Histogenesis in Gastric B-cell Lymphomas

Anti-Helicobacter pylori (HP) therapy succeeded in regressing gastric B-cell lymphomas (gBL) with a close relation to infestation of HP, although the exact mechanism of anti-HP therapy in gBL has not yet been clarified. In order to see a part of the mechanism, this study analyzed stromal cells in 34 gBL cases comprised of 11 cases of mucosa-associated lymphoid tissue (MALT) type and 24 cases of diffuse large B-cell lymphoma (DLBL) by means of immunohistochemistry of CD3, CD5, CD79a, CD68, CD21, S100 protein, thymidine phosphorylase (TP) and inducible nitric oxide synthase (iNOS). Numerous CD68-positive stromal cells were seen in 9 cases of MALT type and 22 cases of DLBL. Many dendritic cells (DC) expressed TP and formed an ill-defined meshwork in the background in 8 cases of MALT type and 17 cases of DLBL. In most cases, transition of CD68-positive stromal cells to DC expressing TP was recognized. There was more or less intermingling of CD3-positive T-cells in all cases. Expression of iNOS was seen in some stromal cells and glandular epithelial cells, but only in 3 cases of MALT type. In the germinal center (GC) colonization of MALT type there were CD21-positive follicular DC, CD68-positive stromal cells, TP-expressing DC and iNOS-expressing cells; whereas in that of DLBL the meshwork of CD21-positive follicular DC was destroyed and the stromal cells did not express TP or iNOS. Then, a peculiar co-existence of intermingling T-cells, CD68-positive stromal cells, DC expressing TP forming an ill-defined meshwork, and lymphoma cells were recognized in gBL. A small number of stromal cells and glandular epithelial cells expressed iNOS and prepared a nitric oxide-rich microenvironment for growth and transformation of MALT type lymphoma cells. This peculiar histogenesis of gBL was thought to explain a part of the mechanism of the anti-HP therapy against gBL.