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
Age
- Most common from ages 5-10
- Rare after age 30
Gender
M:F = 2:1
Associated syndromes
Presentation
- 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
Site
- 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
Size
Variable
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
Matrix
- 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
- 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
Pathology
- 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
Treatment
- 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
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