Rare benign bone lesion (0.1% of bone lesions)

Commonly seen in the proximal femur, calcaneus and ilium

Often incidental finding although can cause discomfort or pain

Milgram histologic stages:

1. Solid tumors with viable lipocytes
2. Some necrosis and focal calcification, but residual viable cells are present
3. Cells have died, cyst formation, new bone formation, secondary to ischemia and infarction

Corresponding radiographic features:

1. Lucent lesions, follow fat attenuation/signal
2. Lucent areas with denser regions of necrosis and calcification
3. More sclerotic borders, increased density, very minimal amount of fat remaining

Differential Diagnosis: Fibrous dysplasia, Unicameral bone cyst, Aneurysmal bone cyst, Liposclerosing myxofibrous tumor, Chondroid tumors