Reactive Paracortical Hyperplasia
Reactive—or diffuse—paracortical hyperplasia (RPH) is characterized by expansion of the paracortical areas of the lymph node. The paracortical/interfollicular zone is rich in T-cells associated with interdigitating dendritic cells and histiocytes. The paracortical zone can undergo expansion in response to inflammatory and immune reactions that trigger a T-cell response. Possible etiologies of RPH include infectious agents, vaccine administration, immunodysregulatory diseases, and therapeutic drugs. The most common viruses that cause RPH include herpes simplex virus (HSV), Epstein-Barr virus (EBV), and cytomegalovirus (CMV). In a subset of patients with RPH, no etiology is apparent.
KeywordsHerpes Simplex Virus Anaplastic Large Cell Lymphoma Small Lymphocyte Vaccine Administration Littoral Cell
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