Follicular Hyperplasia and Follicular Lymphoma
Stimulation of the humoral immune system causes this phenomenon of follicular hyperplasia. Within lymph nodes, there is appearance of large, round, dark staining B cell-rich germinal centers, which are surrounded by a layer of small, naive, non-activated B cells termed the mantle zone. Within these germinal centers, which represent B cells that have been stimulated with antigen and have begun to replicate, two distinct regions have be delineated. A dark zone containing proliferating large, blast-like B cells termed centroblasts, and a light zone made up of B cells with irregular or cleaved nuclear borders termed centrocytes. What to worry about with follicular hyperplasia, is to rule out follicular lymphoma, which is a very difficult disease entity to discern. Important points to look for would be are the dark and light zones being present, variations in the size and shape of the follicules, and maintainence of normal lymph node architecture and margination. All these aspects are found only in normal lymph nodes, such as with follicular hyperplasia. Any deviation would direct the pathologist to look for markers concerning follicular lymphoma.
1) Robbins and Cotran Pathologic Basis of Disease. Seventh Edition. Kumar, V., Abbas, A.K., and Fausto, N. 2005, Elsevier Inc.