= SINUS HISTIOCYTOSIS WITH MASSIVE LYMPHADENOPATHY

= rare dendritic cell disorder characterized by macrophage proliferation

Age: children and young adults; M >F; predilection for individuals of African descent

Histo:emperipolesis (= phagocytosis of lymphocytes, plasma cells, erythrocytes, PMNs) by histiocytes that show S100 positivity; negative for CD1a + Birbeck granules

[em, Greek= inside, peri = around, polemai = to wander about]

• Lymphadenopathy
  • uptake of gallium and FDG by lymphadenopathy
  • fever, elevated ESR, mild anemia
  • nonspecific imaging appearance of painless lymphadenopathy
  
  Location: cervical >retroperitoneal, mediastinal, axillary, inguinal
• Extranodal disease (50%) in nearly every organ system
  • Head
    • intracranial lesions primarily in the epidural or subdural compartments
    • orbital extraconal soft-tissue mass
  • Neck
    • enhancing polypoid masses / mucosal thickening of occasionally aggressive appearance
    • salivary gland lymphoid hyperplasia
  • Bone: commonly in skull, tibia, femur
    • medullary multicentric lytic lesions ± sclerotic margin
  • Lung mass

Prognosis: overall good with indolent clinical course ± spontaneous resolution