Tumor biology

  • Rare, benign, tumor-like disorder
  • Belongs to a group of disorders of the reticuloendothelial system
  • Also known as Histocytosis X, or Langerhan’s cell histiocytosis (LCH)
  • Involves skeleton as either a solitary lesion or in multiple sites
  • Generally active or aggressive in behavior


  • Most common from ages 5-10
  • Rare after age 30


M:F = 2:1

Associated syndromes


  • Pain most frequent presenting symptom
  • Pediatric patient may present with limp, back pain, or scoliosis

Physical findings

  • Palpable mass may be present (rare).
  • Tenderness at site of symptomatic involvement
  • Scoliosis or restricted motion common with spinal lesions

Plain films

  • Single collapsed vertebra in children (vertebra plana)
  • Lytic lesion of long bones or flat bones with variable degree of endosteal and periosteal response (may appear as permeative, aggressive, lytic lesion)
  • Multiple lesions not uncommon
  • Skull, ribs, vertebrae, pelvis and long bones (femur and humerus mostly)
  • Hands and feet almost never affected
  • Ribs more commonly affected in adults; the long bones more commonly affected in children
  • Lesions may be diaphyseal or metaphyseal


Tumor effect on bone
  • Variable
  • Lytic
  • Destruction can be patchy and uneven; more commonly geographic
  • Rib lesions may expand bone as opposed to long bone lesions, where expansion is less common
  • Pathologic fracture is common in the spine (vertebra plana)
Bone response to tumor
  • Usually minimal metaphyseal sclerosis
  • May be periosteal reaction in response to an endosteal erosive lesion
  • Onion skinning may be present
  • Generally no matrix at presentation in symptomatic phase
  • Can have a hazy matrix during the resolution phase; results from bone forming in lytic lesion
  • Cortex may be thinned, scalloped, or have an onion skinned appearance
  • Differential diagnosis for such onion skinning includes eosinophillic granuloma, non-Hodgkin’s lymphoma, and Ewing sarcoma
Soft tissue mass

Rarely present

Differential diagnosis

  • Unicameral bone cyst
    • More commonly larger, less painful, and located in the metaphysis of a bone; eosinophillic granuloma more commonly in diaphysis
  • Osteomyelitis
  • Primary osseous malignancy, such as Ewing sarcoma or lymphoma

Natural history

  • Lesions can progress or disappear over time (can be a few months or longer)
  • Most lesions require diagnostic biopsy, which stimulates resolution of lesion in some cases
  • Persistent aggressive changes may be seen in patients with multiple lesions


  • Gross: Friable tan tissue
  • Microscopic: Infiltrate of histiocytes, Langerhans’ cells, and inflammatory cells
    • Variable numbers of eosinophils present
    • Multinucleated giant cells are seen
  • Langerhans’ cell is diagnostic cell
    • S100 positive on immunohistochemical staining
    • Contains characteristic Birbeck granules (tennis racket-shaped cytoplasmic inclusions) when examined by electron microscopy


  • Lesions typically observed because they often heal spontaneously
  • Indications for surgery
    • Determine the diagnosis
    • Persistent pain
    • Prevention or treatment of pathologic fracture
  • Curettage and bone graft especially indicated for lower extremity lesions; supplement with internal fixation if patient at risk for fracture
  • Low-dose radiation effective in most lesions, but usually reserved for recalcitrant non-healing or recurrent lesions
  • Multiple lesions or visceral involvement may respond to chemotherapy