The specimen is a clavicle from a child, and shows the upper end expanded by a part-fibrous and
part-cystic structure, in which there are areas of haemorrhage. The periosteum still appears to be
intact, although much of the cortex has been destroyed. As often happens, the histology of lesions
such as this can be equivocal. This lesion showed features suggesting a benign giant cell tumour
of bone, but with features also suggesting an aneurysmal bone cyst.
This patient has been lost to follow-up.