Age / Sex : 18 / F

Age / Sex : 18/F

Chief complaint : Pain on right upper arm

P.I : Slip down 3 weeks ago and pain development, but no work-up

aneurysmal bone cyst

Discussion

Findings:

1)     Plain radiography : osteolytic lesion with cortical break-down and pathologic fracture, and suspected soft tissue mass

2)     T1WI : Low signal intensity intraosseous lesion with soft tissue mass
       Multilocular
       High signal intensity foci, may suggest hemorrhagic foci

3)     STIR : Multilocular, intermediate-to-high signal intensity, with fluid-fluid levels
       Adjacent bone marrow edema

4)     Enhancement : Ring-like enhancement along septa

Differential Diagnosis:

Other primary sarcoma, including osteosarcoma or Ewing’s

Diagnosis:  

Aneurysmal bone cyst (Two times open biopsy)

Discussion:

1)     ABC is a misnomer – ABC is not true cyst, not true aneurysm

2)     ABC consists of large vascular spaces, filled with blood and hemosiderin, and lined with giant cells

3)     Primary or secondary (in a pre-existing benign or malignant bone lesion, such as GCT, osteoblastoma, chondroblastoma, fibrous dysplasia, hamangioma, nonossifying fibroma)

4)     Usually pain or pathologic fracture during second decade of life

5)     Any bone, anywhere within bone
common in metaphysis of long bones (femur, tibia, humerus)

6)     Pathogenesis is still unclear
- posttraumatic, reactive vascular malformation, genetically predisposed bone tumors,  - local circulatory disturbance leading to markedly increased venous pressure and development of a dilated and enlarged vascular bed within affected bone

7)     Plain radiographs show radiolucent, expansile mass without matrix production, often septations

8)     Low SI on T1WI, high SI on T2WI, with low SI fibrous septa, enhancement along cyst walls (or septa), surrounding edema on MRI

9)     Fluid-fluid levels are characteristic, but not specific

10)  Solid ABC and giant cell reparative granuloma have similar histologic findingds, and have been used interchangeably in pathology literatures

11)  In this case, plain radiograph shows no so typical expansile appearance. On MRI, however, multilocular septated appearance with fluid-fluid levels can suggest ABC.

References:

1)     Cotalorda J, Bourelle S. Modern concepts of primary aneurysmal bone cyst. Arch Orthop Trauma Surg 2007; 127:105-114

2)     Wootton-Gorges SL. MR imaging of primary bone tumors and tumor-like conditions in children. Magn Reson Imaging Clin N Am 2009; 17:469-487

3)     Ilaslan H, Sundaram M, Unni KK. Solid variant of aneurysmal bone cysts in long tubular bones: Giant cell reparative granuloma. AJR 2003; 180:1681-1687

4)     Keenan S, Bui-Mansfield LT. Musculoskeletal lesions with fluid-fluid level: A pictorial essay. J Comput Assist Tomogr 2006; 30:512-524