lymph node follicle marginal zone
Histologically, the marginal zone pattern of the lymph node is characterized by lymphoid follicles with three distinct layers. The inner layer is composed of follicular center zones, the middle layer of darkly stained mantle zones, and the outer layer of marginal zones. However, the marginal zone pattern is rarely seen in reactive lymph nodes except for mesenteric lymph nodes. Lymph node marginal zones are populated by marginal zone B cells which express CD19 and CD20 and have the phenotypic features of memory B cells.