Age / Sex : 14 / F

Age / Sex: 17 / F

aneurysmal bone cyst

Discussion

Findings:

1) L-spine AP / lateral:

- Well-defined osteolytic lesion of left lamina and spinous process of L4

2) CT

- Expansile osteolytic bone lesion with cortical thinning of left lamina and spinous process of L4

3) MR

- Lobulated mass lesion is noted at left lamina and spinous process of L4

- T1WI: diffuse low SI with multifocal high SI

- T2WI: multiple fluid-fluid levels

- Fat-suppressed enhanced T1WI: heterogeneous enhancement.

Differential Diagnosis:

- Giant cell tumor / Simple bone cyst / chondroblastoma

Diagnosis:  Aneurysmal bone cyst

Discussion:

- Benign bone lesion of unknown origin

- 1.4 ~ 2.3% of primary bone tumors

Clinical features

- 80% of affected patients: < 20 years

- Pain and swelling (weeks to years), sign and symptoms related to compression of spinal cord and/or nerve roots

- Involvement of long tubular bones and spine: 60 ~ 70%

- Involvement of spine: 3 ~ 20% of cases (thoracic > lumbar > cervical > sacrum)

Radiologic feature (spine)

1. Plain radiograph

- Osteolytic and expansile

- Involvement of posterior elements (extension into vertebral body: 75% of cases)

2. CT

- Osteolytic and expansile lesion

- Fluid level (35%)

3. MR

- Expansile and lobulated or septated lesion

- A thin, well-defined complete, or less commonly, incomplete rim of low signal intensity about aneurysmal bone cyst is common

- Inhomogeneity of signal intensity is encountered, and individual lobules of lesion may have markedly different signal intensity characteristics

- Periosseous edema (in some cases)

- Fluid levels within the lesion

References:

1. Diagnosis of bone and joint disorders. Saunders, 2002, 4^th ed. p 4035-4052