Good case of an uncommon solitary lytic bone lesion.
This has the 4 hallmarks elaborated in Brandt and Helms:
- occurs only with a closed growth plate
- abuts articular surface: 84-99% come within 1 cm of the articular surface 1
- well defined with non-sclerotic margin (though < 5% may show some sclerosis 8)
As with most bone tumors, this is not a slam dunk as there are always mimics ranging from fibrous dysplasia to metastatic disease.
chondroblastoma: epiphyseal, usually in skeletally immature patients
- chondromyxoid fibroma: metaphyseal, with a well defined sclerotic margin, multiloculated bubbly appearance 3
aneurysmal bone cyst (ABC): younger age group, but may co-exist with GCT; fluid-fluid levels non-ossifying fibroma: usually younger age group 4
- brown tumour: in the setting of hyperparathyroidism
enchondroma: only really a consideration in lesions of small bones of the hand and foot 3 haemophilic pseudotumour chondrosarcoma: typically older age group
- metastases and multiple myeloma, (always add lymphoma here. Like syphilis and sarcoidosis it can mimic everything).
intraosseous ganglion cysts
- desmoplastic fibroma