Classification Of Histiocytosis
Constitutes diverse group of disorders characterized by prominent proliferation or accumulation of monocyte-macrophage (myeloid) cells. Classification relies on histopathologic, clinical, and genetic findings.
Current Systematic Classification
Modern classification divides histiocytosis into five main groups based on clinical and genetic presentation.
| Group | Category | Specific Disorders |
|---|---|---|
| L | Langerhans-Related | - Langerhans cell histiocytosis (LCH) (Single system, pulmonary, multisystem with/without risk organs) - Erdheim-Chester disease - Extracutaneous/disseminated juvenile xanthogranuloma (JXG) with MAPK mutations |
| C | Cutaneous And Mucosal | - Histiocytoses with cutaneous or mucosal involvement |
| R | Rosai-Dorfman-Destombes | - Familial- Sporadic classical (with/without IgG4 )- Sporadic extranodal |
| M | Malignant Histiocytoses | - Primary phenotypic subtypes - Secondary phenotypic subtypes |
| H | Hemophagocytic Lymphohistiocytoses | - Primary - Sporadic - Unknown |
Traditional Histopathologic Classification
Historically categorized into three distinct classes based on cellular origin and behavior.
| Class | Cell Of Origin | Specific Disorders |
|---|---|---|
| Class I | Dendritic Cell Disorders | - Langerhans cell histiocytosis (LCH)- Juvenile xanthogranuloma- Solitary histiocytoma with dendritic phenotype |
| Class II | Macrophage-Related Disorders | - Hemophagocytic lymphohistiocytosis (HLH) (Primary and secondary) - Rosai-Dorfman disease - Solitary histiocytoma with macrophage phenotype |
| Class III | Malignant Histiocyte Disorders | - Monocyte related leukemias - Extramedullary monocytic tumors - Dendritic cell/macrophage related histiocytic sarcoma |