Case report illustrating evolution of an intraosseous lipoma: Radiology findings and differentials

A 21 year old female patient presented with mild left ankle pain for 2 months. Left ankle radiograph was performed, showing a lucent lesion with narrow zone of transition at anterior body of the calcaneus. Further evaluation with MRI showed T1 hypointense and T2 hyperintense signals within said lesion, with fluid-fluid level. The working diagnosis was aneurysmal bone cyst. Follow-up MRI performed 3 years later showed predominant macroscopic fat within the lesion. This case demonstrates composition change of intraosseous lipoma over time.