Intraosseous lipomas: radiologic and pathologic manifestations.

Sixty-one cases of surgically treated solitary intraosseous lipoma were staged into three categories depending on the degree of involution present histologically: stage 1, tumors of viable fat cells; stage 2, transitional cases composed partly of viable fat cells but also demonstrating fat necrosis and calcification; and stage 3, lesions demonstrating necrotic fat, calcification of necrotic fat, variable degrees of cyst formation, and reactive woven bone formation. Each of these stages had radiologic features that could be correlated with the histopathologic findings in the excised tissue. Examples of stage 3 lesions have frequently been misdiagnosed as unusual bone infarcts or other lesions. Intraosseous lipoma may be a less rare lesion than has previously been suggested.