A benign reactive lymph node. At the top is the capsule. Beneath the capsule is the paracortical zone interrupted by lymphoid follicles; these consists of a pale germinal centre surrounded by a dark blue mantle (cuff) of small, mature lymphocytes.
Reactive follicular hyperplasia lymph node
At higher power one of the reactive follicles is seen. The pale color of the germinal center is due to its content of larger lymphoid cells & macrophages. At the lower right is the subcapsular sinus.
A, Low-power view showing marked differences in size of germinal centers, their well-circumscribed character, and the fact that they are surrounded by a well-defined mantle. B, High-power view of the germinal center showing numerous "tingible-body" macrophages admixed with follicular center cells.
Reactive follicular hyperplasia lymph node
Paracortical hyperplasia, identified by the prominence of postcapillary venules.
Lymph node: Paracortical hyperplasiaSinus histiocytosis (Reactive sinus hyperplasia)
There is a marked increase in the number of macrophages in the lymph node sinuses. Two medullary lymphatic sinuses are shown. They are greatly distended, and their lumens filled with large numbers of large histiocytes with pinkish cytoplasm. The small dark-staining cells accompanying the macrophages are lymphocytes. The medullary lymphoid tissue outside the sinuses consists of small lymphocytes, plasma cells and histiocytes.Multiple adjacent, well-defined, rounded granulomas. A granuloma is a focus of chronic inflammation consisting of a microscopic aggregation of macrophages that are transformed into epithelioid cells surrounded by a collar of mononuclear leukocytes, principally lymphocytes and occasionally plasma cells.
Granulomatous Lymphadenitis