Age / Sex : 13 / F

Age / Sex : 13/F

Chief complaint : ankle pain for 6 months.

osteoid osteoma

Discussion

Findings: Plain ankle lateral view : sclerotic change in upper part of the calcaneus.

 CT : round 1cm type IB osteolytic lesion in upper part of calcaneus with surrounding marrow sclerotic change. There are multiple dot like calcifications within the lesion.

 MRI : T2 sagittal image show a well defined heterogeneous low to high signal intensity lesion in upper part of the calcaneus with diffuse low signal intensity in surrounding marrow. There is high signal intensities in the cervical ligament.

Differential Diagnosis: Enchondroma because of the calfication pattern. But enchondroma is very rare in calcaneus. And surrounding diffuse sclerosis in marrow is not compatible with enchondroma.

Diagnosis:  Osteoid osteoma in calcaneus

Discussion: About 2 to 15% of Osteoid osteoma occurring in the foot. The talus is most common site for osteoid osteoma in foot, and the calcaneus is the next.

Calcaneal osteoid osteoma is arising in upper part as in this case.

Radiographically, osteoid osteoma in the cortex appears as a radiolucent nidus less than 1 cm and surrounded by extensive sclerosis.

In this case, the calcification pattern(diffuse scattering) is unusual for classic osteoid osteoma which is central.

References:

 pp. 240 – 242, Imaging of Bone Tumors, Morrie E.Kricun, W.B. Saunders company