Mantle zone
Summary
The mantle zone is the thin rim of small, resting naïve B lymphocytes surrounding the germinal center of a secondary lymphoid follicle. It expresses CD5, CD20, and cyclin D1 (in neoplastic transformation), and is clinically significant as the cell of origin for mantle cell lymphoma.
Detail
Lymph node and splenic white pulp follicles consist of a germinal center (site of B-cell proliferation, somatic hypermutation, and class switching) surrounded by the mantle zone, composed of small, mature, naïve IgM/IgD-positive B lymphocytes that have not yet undergone germinal center reaction. Outside the mantle zone lies the marginal zone (more prominent in spleen), containing memory B cells and marginal zone B cells involved in T-independent immune responses. Mantle cell lymphoma arises from naïve B cells of the mantle zone and is characterized by the t(11;14) translocation, leading to overexpression of cyclin D1 (BCL1), which drives the cell cycle from G1 to S phase. Immunohistochemically, mantle cell lymphoma is CD5+, CD20+, CD23- (helping distinguish it from CLL/SLL, which is CD5+CD23+), and cyclin D1+. Clinically, mantle cell lymphoma often presents with widespread lymphadenopathy, splenomegaly, and GI involvement (lymphomatous polyposis), and tends to have an aggressive clinical course despite a low proliferative histologic appearance. Understanding the normal architecture of the lymphoid follicle (germinal center → mantle zone → marginal zone) is essential for differentiating reactive processes from lymphomas based on the zone of origin.
Sources
- Robbins and Cotran Pathologic Basis of Disease
- Goljan Rapid Review Pathology
- First Aid for the USMLE Step 1
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