Reactive lymph nodes in pediatric practice.

A variety of unusual reactive conditions may be seen in lymph nodes from the pediatric age group. Some of these, such as the autoimmune lymphoproliferative syndrome, reflect underlying abnormalities of the immune system and cellular control processes, while others are related to viral infections or are of unknown cause. Many of these conditions can mimic malignant neoplasms, so it is important that pathologists recognize these unusual reactive patterns.