Introduction

  • Usually affects young adults
  • Mean age at diagnosis is 28 years
  • Variable duration of symptoms prior to diagnosis
  • Prognosis better than with conventional osteosarcoma


Location

Majority of tumors located in long bones, principally in metaphyseal region, less commonly in diaphysis


Plain films

Size

Usually large


Tumor effect on bone

Lytic lesion with internal trabeculations and variable degrees of internal sclerosis


Bone response to tumor

Generally poorly defined with  wide zone of transition; may demonstrate sharp, well-demarcated margins, however


Cortex

Lesions generally contained within bone without soft tissue extension or periosteal reaction


Pathology

  • Microscopic: Lesions may be difficult to differentiate from fibrous dysplasia
  • Well-formed trabeculae in variably cellular fibrous stroma
  • Cytological atypia usually minimal
  • Absence of osteoblasts and osteoclasts rimming trabeculae and infiltration between pre-existing bone trabeculae supports malignant diagnosis


Differential diagnosis

  • Fibrous dysplasia
  • Fibrosarcoma
  • Infection
  • Lymphoma


Complications

Pathologic fracture (rare)