Lymphoid follicles appearing in gastric mucosa, especially in reactive lymphoid hyperplasia and malignant lymphoma.

Histopathological analysis of reactive lymphoid hyperplasia (RLH) and malignant lymphoma (ML) of the stomach was made based on the observations of lymphoid follicles appearing in gastric mucosa. The materials used for study consisted of 28 stomachs without RLH or tumor obtained from either operation or autopsy, 18 stomachs with RLH, and 46 stomachs with ML. Lymphoid follicles appeared soon after birth, increased with mucosal atrophy, and decreased in mucosa with intestinal metaplasia. They possessed a sinusoidal structure and appeared in the muscularis mucosae intimately related to the lymphatic flow. Excepting for the significant proliferative nature, the structural evolution of lymphoid follicles in RLH was similar to that in atrophic mucosa. They showed, however, a wide spectrum of changes containing cases with simple reactive changes to those with prelymphomatous changes. As to ML, the large cell type demonstrated a destructive proliferation, while both small and medium-sized cell types showed proliferation and infiltration preserving their original structure. In the superficial type, ML was frequently accompanied by RLH and mucosal atrophy. The histological features of ML consisted of not only the characteristics of tumor cells but also the proper mucosal changes including lymphoid follicles.