Presumed recurrent chondromyxoid fibroma of the proximal humerus.

The differential diagnosis is:

• Aneurysmal bone cyst (ABC):  fluid/fluid level, periosteal reaction, no matrix mineralization. Chondromyxoid fibroma with secondary ABC is not uncommon.
• Fibrous dysplasia: central location, no internal septation or periosteal reaction. Ground glass attenuation is typical.
• Adamantinoma: older patient, vast majority in the upper tibia, cortical destruction with aggressive periosteal reaction.
• Fibrous cortical defect (FCD) and non-ossifying fibroma (NOF): Possible mild cortical expansion, no destruction or periosteal reaction, not painful.