Epidemiology
This is an uncommon benign bone tumor made up of mature fat inside the bone. It is most often located in the calcaneus (the heel bone) and in the proximal femur, and it can also appear in other long bones. It mainly affects adults and is often discovered by chance on a radiograph requested for another reason.
Basic features
It frequently causes no symptoms. When it does, the usual picture is mild local discomfort or pain, especially in the heel. On the radiograph it appears as a lucent lesion with well-defined margins, often with a characteristic central calcification, because over time the fat inside can involute and leave calcium or a small cyst behind: that is why its appearance varies considerably from case to case. What confirms the diagnosis is MRI, where the contents show the same signal as subcutaneous fat.
Usual treatment
An asymptomatic intraosseous lipoma with a typical appearance requires no treatment and no follow-up. When it causes persistent pain, when thinning of the bone raises concern about a fracture, or when the diagnosis is unclear, curettage —scraping the lesion out from inside the bone— is considered, with bone graft or a bone substitute if a significant cavity is left.
Outcomes and prognosis
The prognosis is excellent. After a complete curettage recurrence is uncommon and functional recovery is usually good; transformation into a malignant tumor is exceptional.