General:
Idiopathic proliferation of histiocytes
EG usually between 5 and 15 years
Benign disease limited to bone or lung
Slightly elevated alkaline phosphatase
CT, MRI and bone scans are sensitive, but not specific
Radiography:
Commonly seen as lytic, modestly destructive lesion of flat bone, as skull, mandible, ribs, and pelvis (more than 50%)
Skull:
Well defined lytic lesions with sharp borders, “punched out lesions”, measure 1–4 cm
Heals with a small, residual bone fragment or sequestrum (DD: osteomyelitis)
Rib:
Rare Usually within medullary cavity Regress on their own
Spine:
Vertebra plana with sparing of posterior elements and preservation of disc spaces
Pelvis:
Illdefined lytic lesions
Well circumscribed when mature
Long bones:
Often diaphysis of femur, tibia, humerus
May be in metaphysis or extend to the physis and epiphysis
Isolated epiphyseal involvement is rare
From 4 cm to 6 cm
Show endosteal scalloping without cortical break or soft tissue mass.
In early stage periosteal reaction or permeative lysis may give aggresive look
References:
1. Hughes et al. Benign primary tumours of the ribs. Clin rad (2006): 61:314-322
2. Hoover BK et al. Langerhans cell histiocytosis. Skeletal Radiology 2007: 36: 95-104
