Lymphoid hyperplasia

Lymphoid hyperplasia (or Lymphoid hypertrophy) is the rapid growth proliferation of normal cells that resemble lymph tissue.

Lymph Node Anatomy
The lymph node is a round or reniform organ that is usually no larger than 1cm in diameter. It is composed of a cortex, paracortex, and medulla with sinuses distributed throughout. The paracortex is known as the T-cell zone due to the presence of T-cells, and the cortex is composed of follicles of B cells and is known as the B-cell zone. Each of these locations can undergo hyperplasia.

Follicular Hyperplasia
Follicular hyperplasia is a stimulation of the B cell compartment. It is caused by an abnormal proliferation of secondary follicles and occurs principally in the cortex without broaching the lymph node capsule. The follicles are cytologically polymorphous, are often polarized, and vary in size and shape. Follicular hyperplasia must be distinguished from follicular lymphoma (bcl-2 protein is expressed in neoplastic follicles, but not reactive follicles).

Paracortical Hyperplasia
Paracortical hyperplasia in the preferential stimulation of the T cell compartment. It is caused by an abnormal expansion of the interfollicular zones but is confined within the lymph node capsule. The population of the compartment is cytologically polymorphous. Paracortical hyperplasia may be accompanied by vascular proliferation. Must be distinguished from monomorphous T cell lymphoma.

Sinus Hyperplasia
Sinus hyperplasia is the preferential stimulation of the histiocytic (tissues macrophage) compartment. Histological features include distention or engorgement of both subscapular and inatraparenchymal sinuses by benign histiocytes which may be hemophagocytic. Sinus hyperplasia may be associated with non-hematolymphoid malignancy. Other features include presence of white spaces and lymphocytes(large cells) within sinuses.

Complications
It is one common source of appendicitis, as it may cause an obstruction of the appendiceal lumen, resulting in the subsequent filling of the appendix with mucus, causing it to distend and internal pressure to increase.