Benign Lymphadenopathy

Benign lymphadenopathy is encompassed by all non-neoplastic processes occurring in a lymph node showing varying degrees of reactive changes, e.g., follicular, parafollicular/interfollicular, or mixed follicular and paracortical hyperplasia; progressive transformation of germinal centers (PTGCs); granulomatous or necrotic changes; vascular transformation; drug inducted (iatrogenic); foreign-substance deposition (lipid, silicone, metal, gold, and proteinaceous materials); and lymphadenopathies associated with clinical syndromes (e.g., Kimura, Rosai–Dorfman, rheumatoid, dermatopathic, Castleman, Kikuchi–Fujimoto, systemic lupus, and IgG4 lymphadenopathy). Following the emergence of advanced molecular diagnostic techniques, especially implication of next-generation sequencing (NGS) in clinical laboratories and research, people have better insights into non-neoplastic lymphadenopathies. Among them, several previously benign lymphadenopathy disorders (LPD) are now included in the fifth the edition of the WHO Classification of Tumors under “tumour-like lesions with B-cell or T-cell predominance.” These have been included in this section for completion, but the changes should be noted for the following: