The presence of a fat-containing lesion within the calcaneus represents intraosseous lipoma. The presence of cystic components suggests involuting lipoma. 

Chemical shift artifact are produced at water-lipid interfaces and present with white or black lines at the interface. These artifacts are most commonly seen when a cystic structure is surrounded by fatty tissue. This case nicely presents the chemical shift artifact at the boundary of a water-containing lesion sorrounded by fat.