53 Intraosseus Lipoma

CASE 53

Intraosseus Lipoma

George Nomikos, Mark Murphey, Anthony G. Ryan, and Peter L. Munk

Clinical Presentation

A 32-year-old man presented with foot pain.

Figure 53A

Figure 53B

Figure 53C

Figure 53D

The lateral radiograph of the ankle (Fig. 53A) shows a geographic lytic lesion in the anterior calcaneus with a narrow zone of transition and significant surrounding sclerosis. There is a central area of dense mineralization in the lesion. There is no evidence of pathologic fracture or aggressive bone destruction. CT (Fig. 53B) shows a well-marginated lesion arising in the anterior calcaneus. Note the sclerotic margin and central dense focus of mineralization. The predominant internal attenuation of the lesion is identical to subcutaneous fat. Axial T1- and sagittal fat-suppressed T2-weighted images demonstrate that the majority of the lesion follows fat signal intensity on the T1- and T2-weighted images (Figs. 53C, 53D); however, there is central fluid signal intensity in the lesion, around the area of mineralization.

Diagnosis

Involuting intraosseous lipoma.

Differential Diagnosis

Involuting infarction
Simple bone cyst
Fibrous dysplasia
Aneurysmal bone cyst
Cartilaginous lesions
Liposclerosing myxofibrous tumor (LSMFT)

Discussion

Background

Intraosseous lipomas are uncommon benign bone tumors, accounting for ~0.1% of bone tumors. However, in our opinion and experience, they are much more frequent. Although the radiographic appearance of lesions in the calcaneus is often diagnostic, lesions in other locations may have a more variable appearance (see differential diagnosis list above). Three stages have been described: lesions composed virtually entirely of mature fat cells; lesions composed of mature fat cells, fat necrosis, and mineralization; and lesions demonstrating cyst formation, myxoid degeneration, and reactive woven bone production.