Polyostotic Lesions

B. J. Manaster, MD, PhD, FACR

DIFFERENTIAL DIAGNOSIS

Common

Fibroxanthoma (Nonossifying Fibroma)
Fibrous Dysplasia, Polyostotic
Langerhans Cell Histiocytosis (LCH)
Osteomyelitis
Osteochondroma, Multiple Hereditary Exostosis
Leukemia
Ewing Sarcoma, Metastatic
Metastases, Bone Marrow

Less Common

Lymphoma, Multifocal
Osteosarcoma, Metastatic
Hyperparathyroidism/Renal Osteodystrophy, Brown Tumor
Melorheostosis

Rare but Important

Ollier Disease
Maffucci Syndrome
Chronic Recurrent Multifocal Osteomyelitis
Sarcoidosis
Trevor Fairbank

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Polyostotic nature of lesion can narrow differential substantially and is highly valuable characteristic
- Information regarding multiple sites can be gained by bone scan, PET/CT, or clinical exam
Lesions listed above range from benign (“leave me alone”) lesions → “Aunt Minnie” lesions → highly aggressive lesions
- Most use this alternative approach to sort these out

Helpful Clues for Common Diagnoses

Fibroxanthoma (Nonossifying Fibroma)
- Benign fibrous cortical defects (same histologically as NOF but smaller) are often multiple in children
- Nonossifying fibroma (NOF) not commonly multiple, except in patients with neurofibromatosis
- Both have same natural history of healing
- Both are cortically based and metadiaphyseal
Fibrous Dysplasia, Polyostotic
- Lesion may have different appearance in different locations
  - Skull: Sclerotic
  - Pelvis: Bubbly, lytic
  - Long bones: Generally central, metadiaphyseal, mildly expanded, with variable homogeneous ground-glass density
Langerhans Cell Histiocytosis (LCH)
- Lesions may be lytic, geographic, and nonaggressive
- Lesions may also be extremely aggressive in appearance: Permeative, cortical breakthrough, soft tissue mass, periosteal reaction, with rapid growth
- Hint: Skull lesions may have beveled edge appearance due to differential involvement of inner and outer tables
Osteomyelitis
- Hematogenous spread usually results in metaphyseal sites
- Osteomyelitis can appear extremely aggressive, with permeative change and cortical breakthrough with soft tissue mass; may not be distinguishable from aggressive tumor
- Sickle cell patients at risk for multifocal osseous infection; higher predilection for Salmonella
Osteochondroma, Multiple Hereditary Exostosis
- Not difficult diagnosis if exophytic (cauliflower) lesions are present
- May have only sessile exostoses at metaphyses, which can give appearance of dysplasia; diagnosis often missed
Leukemia
- Diffuse marrow infiltration may result in appearance of osteopenia, easily overlooked
- Metaphyseal lucent bands may highlight degree of osteopenia
- MR shows extent of abnormalities
Ewing Sarcoma, Metastatic
- Primary lesion usually highly aggressive; lytic, permeative, cortical breakthrough, large soft tissue mass
- May have extensive reactive bone formation, giving appearance of osteoid, with potential confusion with osteosarcoma
  - Reactive bone formation restricted to bone, does not extend into soft tissue mass (as it does in osteosarcoma)
- Most common sarcoma to have osseous metastases; lung and osseous metastases present with equal frequency

Helpful Clues for Less Common Diagnoses

Lymphoma, Multifocal
- 50% of childhood bone lymphoma is polyostotic (much less frequent in adults)
- Lesions highly aggressive: Permeative, cortical breakthrough with soft tissue mass
- Generally lytic but may have reactive sclerosis within osseous lesion
- In same differential as Ewing sarcoma with metastases, multifocal osteomyelitis, LCH, and metastases

Alternative Differential Approaches

“Aunt Minnie” lesions can generally be identified immediately
- Fibroxanthoma (nonossifying fibroma)/benign fibrous cortical defect
- Osteochondroma (multiple hereditary exostoses); remember they can be sessile and resemble a metaphyseal dysplasia
- Melorheostosis
- Sarcoidosis (when lacy appearance is obvious)
- Trevor Fairbank
Polyostotic lesions, which are usually monomelic
- Fibrous dysplasia (generally unilateral)
- Melorheostosis
- Ollier disease
- Trevor Fairbank
- Maffucci syndrome
Polyostotic lesions with an intermediately aggressive appearance
- Fibrous dysplasia: Generally central, poorly marginated, but geographic
- Langerhans cell histiocytosis: Appearance ranges from nonaggressive geographic to extremely aggressive permeative
- Hyperparathyroidism/renal osteodystrophy, brown tumor: Generally lesion is geographic, but surrounding bone abnormal in density & trabecular pattern
Polyostotic lesions with aggressive appearance: These can be indistinguishable from one another by imaging
- Langerhans cell histiocytosis: Range in appearance from nonaggressive to highly aggressive
- Osteomyelitis
- Leukemia
- Ewing sarcoma, metastatic
- Metastases, bone marrow
- Lymphoma, multifocal
- Osteosarcoma, metastatic
- Chronic recurrent multifocal osteomyelitis

Image Gallery

Anteroposterior radiograph shows a small lytic cortical lesion

(benign fibrous cortical defect) and a sclerotic healing nonossifying fibroma

. The 2 lesions have the same histology, and the natural history is to heal.

Oblique radiograph in the same patient shows a lytic cortically based lesion; this is another NOF, but 1 which is still active in this child. These images show the 3 different appearances for this lesion.

(Left) Anteroposterior radiograph shows mixed lytic and sclerotic lesion involving the metadiaphysis of the femur, tibia, and fibula. The lesions are central and nonaggressive, typical of fibrous dysplasia. (Right) Anteroposterior radiograph shows the mildly expanded and sclerotic, otherwise featureless “ground-glass” appearance of fibrous dysplasia in the tibial diaphysis