Lymph nodes in gastric B-cell lymphoma: pattern of involvement and early histological changes

This study aims to analyse the histological pattern of nodal involvement in gastric B-cell lymphoma and to detect early involvement of the lymph nodes.

Histological findings of 37 resected primary gastric lymphomas with 1313 regional lymph nodes were analysed. The primary tumour was classified into four groups: MALT lymphoma, MALT lymphoma with a minor large B-cell lymphoma (<20%), large B-cell lymphoma with MALT lymphoma, and large B-cell lymphoma without MALT lymphoma. Histological patterns of nodal involvement were divided into sinusoidal, subsinusoidal/marginal, follicular, and diffuse patterns. Semi-nested polymerase chain reaction (PCR) analysis for IgH gene rearrangement was performed. Nodal involvement was found in 2/13 (15%) MALT lymphomas, 5/6 (83%) MALT lymphomas with a minor large B-cell lymphoma, 9/12 (75%) large B-cell lymphomas with MALT lymphoma, and 6/6 (100%) large B-cell lymphomas without MALT lymphoma. The MALT lymphoma and MALT lymphoma with a minor large B-cell lymphoma showed a predominantly sinusoidal and subsinusoidal pattern, whereas diffuse pattern predominated in large B-cell lymphomas without MALT lymphoma and large B-cell lymphomas with MALT lymphoma. The follicular pattern was least common, being observed in 10.2% of large B-cell lymphomas without MALT lymphoma and large B-cell lymphomas with MALT lymphoma. Sinusoidal obliteration with permeation of small monocytoid cells into subsinusoidal zone is a characteristic finding suggesting early nodal involvement of MALT lymphoma.

Histological patterns of nodal involvement in gastric B-cell lymphoma vary according to the histological grade. Immunostaining for CD20 with or without PCR analysis for IgH gene rearrangement would be a useful ancillary method to confirm lymphomatous involvement.