An expansile intramedullary lesion with a homogeneous ground-glass matrix, a well-defined sclerotic rim (rind) and no periosteal reaction — a "leave-me-alone" lesion in most cases.
Orient first
- Monostotic (ribs, proximal femur, craniofacial) or polyostotic; McCune–Albright with endocrine findings and skin pigmentation.
- Shepherd crook deformity of the proximal femur from repeated fractures.
- Sarcomatous change is rare: new pain, cortical destruction and a soft tissue mass.
Acquire the study
- Radiographs in two planes; CT for craniofacial and complex lesions.
The manoeuvre
- Matrix: ground-glass (smudgy), homogeneous; size in cm.
- Margin: well-defined, thick sclerotic rind; endosteal scalloping without cortical breach.
- Deformity: bowing, shepherd crook.
What confirms it
- Typical imaging in a typical site; biopsy only when atypical.
What licenses you to exclude it
- Cortical destruction or a soft tissue mass excludes uncomplicated fibrous dysplasia — escalate.
The classic misread
- Biopsying a classic lesion unnecessarily.
- Missing optic canal narrowing in craniofacial disease.