Subperiosteal aneurysmal bone cyst

Case contributed by Jeremy Jones

Presentation

Thigh mass. Slow growing over several months.

Patient Data

Age: 11 years
Gender: Female

Peripheral ovoid lucency on the lateral margin of the femoral diaphysis. Cortical thickening at either end. Intermediate appearances warrant additional imaging with MRI.

Subperiosteal ovoid tumor with multiple cysts with fluid-fluid levels. Appearances of an aneurysmal bone cyst.

Pathology report:

Predominantly cystic lesion comprising of septa, reactive woven bone, osteoclast-like giant cells and fibroblastic spindle cells.  

Patchy wispy staining with SMA. 
G34W histone, S100, AE1.3, CD34, ERG and desmin are negative.  
MIB-1 reveals a low proliferation index (<5%).  

FISH: USP6 gene re-arrangement.

Diagnosis: aneurysmal bone cyst.

Case Discussion

Fluid-fluid levels in bone tumors are relatively rare and occur in aneurysmal bone cysts (or tumors with aneurysmal bone cyst changes) and telangiectatic osteosarcoma.

A subcortical diaphyseal location is unusual.

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