Findings:

Multiseptated, eccentric osteolytic lesion involving anterior cortex of the tibia

Soap-bubble appearance

Slightly expansile lesion with focal extraosseous extension

Mild anterior bowing deformity of the tibia

No obvious involvement of bone marrow

Differential Diagnosis:

Adamantionoma (classic)

Osteofibrous dysplasia

Diagnosis:  Differentiated adamantinoma

Discussion:

1. Differentiated adamantinoma

- Osteofibrous dysplasia-like adamantinoma

- Regressing, juvenile

- Deformity-inducing

- Strands of epithelial cell (+) on hematoxylin-eosin stain

2. Adamantinoma (classic)

- Low grade malignancy as a primary bone tumor with epithelial characteristics

- Much less favorable prognosis than differentiated adamantinoma & OFD

- Young adult (mean age 30)

- Midshaft of tibia (85%), synchronous involve of tibia & fibula (10%)

- Osteolytic, eccentric, expansile, multifocal, sclerotic margin

- Soap-bubble appearance

 - Predominant intracortical: possible infiltration into the bone marrow

 - Less common bowing deformity than osteofibrous dysplasia

 - Longitudinal orientation

 - Extracortical extension (15%)

 - Uncertain embryogenesis: epithelial cell surrounded by a fibrous stroma

 - Tubular variant, basaloid variant, squamous variant, spindle cell variant, OFD-like variant, Ewing’s-like variant

3. Osteofibrous dysplasia

- Children

- Common bowing deformity or pseudoarthrosis of the tibia

- Spontaneous regression at puberty

- 25% recurrence after curratage or local resection

    -> recommendation of delayed surgery until after puberty only for extensive lesions

- Intracortical, well-marginated, marginal sclerosis, ground-glass appearance

- Histologic features similar to fibrous dysplasia

- Spicules of woven bone separated by a fibrovascular stroma

- Possible ‘cytokeratin-positive mast cells (+)’ within the fibrous stroma on routine HE stain

   : not epithelial cell

References

1. LB. Kahn. Adamantinoma, osteofibrous dysplasia and differentiated adamantinoma. Skeletal Radiol 2003;32:245-258

2. HJV. Woude et al. MRI of Adamantinoma of Long Bones in Correlation with Histopathology. AJR 2004;183:1737-1744