Secondary Lymphoid Tissues ›› Mucosa-Associated Lymphoid Tissue (MALT) ›› Normal GI Tract (Non-Gastric, e.g. Small Bowel): Mucosa Associated Lymphoid Tissue (MALT)* Click Here for Full Size Additional Image 1 › Microscopic Features: Normal Lymphoid tissue that is associated with certain mucosa such as the small intestinal Peyer's patches As opposed to normal lymph nodes, these Mucosa Associated Lymphoid Tissue or MALT are not encapsulated Similar to lymph nodes, they are comprised of follicles (primary and secondary) and interfollicular areas The primary follicles (not antigen stimulated and lacks a germinal center) and secondary follicles (antigen stimulated with a germinal center in the middle) are the B-cell zones The interfollicular (between follicles) areas are the T-cell zones › Normal % blood-PB, marrow-BM, lymphoid tissue-LN: PB: N/A BM: N/A LN: N/A › May Resemble: Mantle Cell Lymphoma Normal reactive Lymph node Normal Mucosa Associated Lymphoid Tissue (MALT) Normal Spleen › Differential Diagnoses: Follicular lymphoma Mantle Cell Lymphoma Reactive lymphoid hyperplasia › Classic Immunophenotype: "T"-cells have the "Tiny" CDs: CD2, CD3, CD4, CD5, CD7, CD8 "B"-cells have the "Bigger" CDs: CD19, CD20, CD22 › Misc: Similar to lymph nodes and the spleen, the primary follicles (not antigen stimulated and lacks a germinal center) and secondary follicles (antigen stimulated with a germinal center in the middle) are the B-cell zones and the the interfollicular (between follicles) areas are the T-cell zones