Histiocyte Society classification of histiocytoses

Last revised by Yuranga Weerakkody on 22 May 2020

The Histiocyte Society classification of histiocytoses and neoplasms of macrophage-dendritic cell lineages is currently in its 2016 revision of the organization's initial classification system from 1987.


Histiocytes are mononuclear phagocytes that reside in tissues, including macrophages and dendritic cells. Histiocytoses are disorders characterized by the accumulation of cells derived from macrophages or dendritic cells.


L (Langerhans) group
C group: cutaneous and mucocutaneous non-Langerhans cell histiocytoses
M group: malignant histiocytoses
  • primary malignant histiocytoses
  • secondary malignant histiocytoses (following or associated with another hematologic neoplasia)
  • subtypes
    • histiocytic
    • interdigitating cell
    • Langerhans cell
    • indeterminate cell
    • not specified
R group: Rosai-Dorfman disease and miscellaneous noncutaneous, non-Langerhans cell histiocytoses
  • familial Rosai-Dorfman disease
  • sporadic Rosai-Dorfman disease
    • classical (nodal) Rosai-Dorfman disease
    • extranodal Rosai-Dorfman disease
    • neoplasia-associated Rosai-Dorfman disease
    • immune disease-associated Rosai-Dorfman disease
  • other non-C non-L non-M non-H histiocytoses
H group: hemophagocytic lymphohistiocytosis and macrophage activation syndrome
  • primary hemophagocytic lymphohistiocytosis (Mendelian inherited conditions)
  • secondary hemophagocytic lymphohistiocytosis (apparently non-Mendelian)
  • hemophagocytic lymphohistiocytosis of unknown/uncertain origin

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