DESCRIPTION

• Any lesion that is detected in the bone, either by physical examination or radiographic studies
• The lesion may or may not have originated in the bone. Most bone lesions seen in children are benign, but a significant minority is malignant and requires intensive therapy. Even so, benign bone lesions can be locally aggressive and cause significant morbidity while not being overtly malignant (i.e., metastasize).

EPIDEMIOLOGY

• The incidence of benign bone tumors is difficult to estimate. Many are diagnosed only radiographically and are never biopsied.
• The majority of bone masses seen in children are benign.
• Primary malignant bone tumors account for 6–7% of newly diagnosed cancers in children.
  • There are approximately 700 to 800 new primary bone cancers diagnosed in children every year in the United States.
  • Osteosarcoma is the most common with about 400 new cases each year.
  • Ewing sarcoma is the second most common with about 300 cases each year in the United States.

ETIOLOGY

• Based on patient age
  • 0 to 10 years
    • Benign
      • Bone cyst (simple)
      • Langerhans cell histiocytosis (LCH)/eosinophilic granuloma
    • Malignant
      • Ewing sarcoma
      • Metastatic disease/leukemia
  • 10 to 20 years
    • Benign
      • Nonossifying fibroma
      • Fibrous dysplasia
      • Bone cysts, simple and aneurysmal
      • Osteochondroma
      • Osteoid osteoma
      • Osteoblastoma
      • Chondroblastoma
    • Malignant
      • Osteosarcoma
      • Ewing sarcoma
      • Adamantinoma
      • Metastatic disease
• Based on location
  • Epiphysis
    • Chondroblastomas
    • Giant cell tumor of bone
  • Metaphysis
    • Osteosarcoma
    • Osteoblastoma
    • Bone cysts
    • Osteochondroma
    • Nonossifying fibroma
    • Osteoid osteoma
  • Diaphysis
    • Ewing sarcoma
    • Fibrous dysplasia
    • Adamantinoma
    • Osteoid osteoma
    • Metastatic lesions

RISK FACTORS

Several disease states predispose a patient to develop bone lesions.

• Hereditary multiple osteochondromas/hereditary multiple exostoses: autosomal dominant germline mutations in EXT1 and EXT2
• Ollier disease: multiple enchondromas (unilateral) associated with IDH1/IDH2 mutations
• Maffucci syndrome: multiple enchondromas (bilateral) with vascular malformations associated with IDH1/IDH2 mutations
• McCune-Albright syndrome: fibrous dysplasia (usually in multiple bones) with café-au-lait spots and endocrine abnormalities; defects in GNAS1 gene
• Mazabraud syndrome: fibrous dysplasia (usually polyostotic) with soft tissue myxomas associated with defects in GNAS1 gene
• The following syndromes predispose patients to osteosarcoma:
  • Hereditary retinoblastoma: Rb gene mutation
  • Li-Fraumeni syndrome: TP53 mutation; patients are also at increased risk for other sarcomas and brain tumors.
  • Werner syndrome: RECQL2/WRN mutation; skin changes associated with premature aging, short stature, bilateral cataracts
  • Bloom syndrome: RECQL3/BLM mutation; sensitivity to sunlight, short stature, mild microcephaly, café-au-lait spots, predisposition to cancers
  • Rothmund-Thomson syndrome: RECQL4 mutation; characteristic skin changes, juvenile cataracts, skeletal dysplasia, skin cancer