Bubbly Bone Lesion

Christopher G. Anton, MD

DIFFERENTIAL DIAGNOSIS

Common

Nonossifying Fibroma (NOF)

Less Common

Aneurysmal Bone Cyst (ABC)
Unicameral Bone Cyst (UBC)
Fibrous Dysplasia (FD)
Langerhans Cell Histiocytosis (LCH)
Enchondroma
Primary Sarcoma or Metastatic Disease

Rare but Important

Osteoblastoma
Giant Cell Tumor (GCT)
Chondroblastoma
Chondromyxoid Fibroma (CMF)

ESSENTIAL INFORMATION

Helpful Clues for Common Diagnoses

Nonossifying Fibroma (NOF)
- a.k.a. fibroxanthoma, fibrous cortical defect (FCD)
- Developmental defect, usually discovered as incidental finding on radiograph or MR of knee
- Age: 2-20 years
- M:F = 2:1; 30-40% of all children
- Diametaphyseal of long bones
  - Femur (38%), tibia (43%), knee (55%), fibula (8%), humerus (5%)
- Eccentric, multiloculated, subcortical; no mineralized matrix; cortex may appear absent; scalloped sclerotic margin
  - Size differentiates FCD and NOF
  - FCD: < 2 cm, within cortex
  - NOF: > 2 cm, extends into medullary cavity
- T1WI: Hypointense with hypointense rim (sclerotic margin)
- T2WI: Low to intermediate intensity with hypointense rim (sclerotic margin)
- T1 C+: Enhances
- Jaffe-Campanacci syndrome
  - Café-au-lait lesions, mental retardation, hypogonadism, ocular and cardiovascular abnormalities
- Usually asymptomatic and requires no treatment
- Most spontaneously regress with time, progressive ossification
- Curettage and bone grafting if lesion is > 50% diameter of weight bearing bone; increased risk of pathologic fracture

Helpful Clues for Less Common Diagnoses

Aneurysmal Bone Cyst (ABC)
- Not true neoplasm: Intraosseous AVM
- Thin-walled, blood-filled cystic cavities
- Age: 10-30 years; rare in ≤ 5 years old; slight female predominance
- Primary (1°) or secondary (2°) in preexisting lesion in 1/3 of cases
  - 1°: No recognized preexisting lesion
  - 2°: GCT, chondroblastoma, fibrous dysplasia, osteoblastoma, chondromyxoid fibroma, NOF
  - 2°: Osteosarcoma (e.g., telangiectatic variant), chondrosarcoma, malignant fibrous histiocytoma
- Typically metaphyseal, most commonly around knee
- Tubular long bones (70-80%), lower leg (29%), pelvis (5-10%), clavicle and ribs (5%), spinal posterior elements (16%)
- Geographic eccentric expansile lucent lesion ± multiloculated, markedly thinned cortex (may need CT to see) ± periosteal reaction (if fractured)
- MR: Characteristic fluid-fluid level (blood products) containing cavities of differing signal intensity; hypointense rim surrounds ABC
  - Enhancement of cyst walls and septations without enhancing cyst contents, “honeycomb”
- Treatment: Curettage and bone grafting with 20% recurrence rate
Unicameral Bone Cyst (UBC)
- a.k.a. simple or solitary bone cyst
- Age: 10-20 years; ˜ 2/3 present with pathologic fracture
- Proximal humerus and femur in up to 80-90%
- Central metaphyseal, well defined, lucent, lacks periosteal reaction unless fractured
- Hint: Pathognomonic, fallen fragment sign
  - Pathologic fracture with cortical bone fragment floating dependently with UBC
- MR: May contain fluid-fluid level if traumatized; no solid enhancing component
Fibrous Dysplasia (FD)
- Age: 5-20 years, peak 10-20 years
- Monostotic (70-80%) or polyostotic
- Expansile, ground-glass, lucent, sclerotic (skull base lesions), no periosteal reaction, bowing
- Associations
  - McCune-Albright: Female predominance, polyostotic, unilateral FD, precocious puberty, hyperthyroidism, café-au-lait spots
  - Mazabraud syndrome: Polyostotic FD with intramuscular myxoma, rare
Langerhans Cell Histiocytosis (LCH)
- Age: 50% < 10 years
- Lytic, sharply demarcated lesion without sclerotic margin unless healing
- Skull (50%), axial skeleton (25%), proximal long bones (15%)
Enchondroma
- Age: 10-30 years
- Lucent, scalloped endosteum; ring and arc calcified matrix
- Small bones of hand and wrist; metadiaphysis of long bones
Primary Sarcoma or Metastatic Disease
- Telangiectatic osteosarcoma: Radiographically, lytic lesion could look like ABC

Helpful Clues for Rare Diagnoses

Osteoblastoma
- Age: 80% < 30 years old
- 1-10 cm in size, > 1.5 cm osteoblastoma, < 1.5 cm considered osteoid osteoma
- Lytic, expansile, sclerotic margin, variable central calcification, radiolucent nidus
- Spine (40%), long bones (30%), hands and feet (15%), skull and face (15%)
- May present with painful scoliosis
- Extensive inflammatory change can mimic malignancy or infection
Giant Cell Tumor (GCT)
- Occurs after growth plate closure
- Metaepiphyseal, eccentric, lytic, nonsclerotic margin, extends subarticular bone ± periosteal reaction
- Long bones (75-90%), around knee (50%)
- Pathologic fracture (30%)
Chondroblastoma
- Eccentric, epiphyseal, expansile; periosteal reaction in 50%
- Immature skeleton
- Most commonly around knee and proximal humerus
  - Long bones (80%), hands and feet (10%)
- Thin sclerotic margin with chondroid calcification in 1/3
- MR: Solid with no fluid-fluid levels
  - T1WI: Low to intermediate
  - T2WI: Intermediate to low with surrounding edema
Chondromyxoid Fibroma (CMF)
- Eccentric, lucent with sclerotic margin
- Male predominance; CMFs present with pain
- Treatment: Curettage, recurrence in 25%

Image Gallery

Anteroposterior radiograph shows a bubbly eccentric lesion

with a scalloped sclerotic margin within the distal tibial diaphysis. Notice the thinned cortical margin

of the NOF.

Anteroposterior and oblique radiographs show an eccentric, multiloculated, lucent lesion

with a thin sclerotic margin within the distal tibia. Notice the thinned lateral cortical margin

(Left) Anteroposterior radiograph shows an eccentric lucent lesion

with a thin sclerotic scalloped margin within the proximal lateral aspect of the tibia. NOFs are most commonly seen about the knee. (Right) Lateral radiograph in the same child shows the NOF