Secondary Lymphoid Tissues ›› Mucosa-Associated Lymphoid Tissue (MALT) ›› Normal

GI Tract (Non-Gastric, e.g. Small Bowel): Mucosa Associated Lymphoid Tissue (MALT)*


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› 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 [Compare]
• Normal reactive Lymph node [Compare]
• Normal Mucosa Associated Lymphoid Tissue (MALT) [Compare]
• Normal Spleen [Compare]

› 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