CASE 49
By: Dr. Mai Mattar, MD and Dr. Nizar Al-Nakshabandi MD, FRCPC
HISTORY: 30-year-old male with foot pain.
What are your findings?
What is the differential diagnosis?
What are the causes?
FINDINGS:
(A) Oblique and AP views of the left foot demonstrate a destructive lesion within the medial aspect of the talar head extending into the subarticular aspect with a narrow zone of transition and well-defined sclerotic borders.
(B) Axial T1, PDFS, and post contrast studies with axial bone window of a CT scan demonstrate an expansile lesion which appears low in signal on T1, bright on PDFS with multiple fluid-fluid levels and heterogenous post contrast enahancement. The medial cortex of the talar head is distructed and the lesion extends to the adjacent soft tissue. Otherwise the lesion appears well-defined with a narrow zone of transition. No calcification or ossification on CT.
DIFFERENTIAL DIAGNOSIS:
Aneurysmal bone cyst, unicameral bone cyst. Other sinister lesions with fluid-fluid level such as telangiectatic osteosarcoma should be considered. Osteoblastoma, chondroblastoma and GCT.
DIAGNOSIS:
Aneurysmal bone cyst (biopsy proven).
PEARLS AND DISCUSSION:
Disease of childhood and adults.
Pathologically it is fluid filled spaces of variable size separated by connective tissue.
It can be primary or secondary to an underlying lesion such as fibrous dysplasia, giant cell tumor, chondroblastoma or even osteosarcoma.
It typically occurs in long bones in up to 60% of the patients in the metaphysis. Furthermore, up to 30% occur in the spine and sacrum. Epiphyseal or apophyseal involvement is rare.
Imaging characteristics as shown in the example here.
Treated by curetting the bone and grafting is a traditional way of treatment with recurrence rate of up to 20%.
Interventional radiology has a role by percutaneous injection of fibrosing agents [calcitonin and Methylprednisolone, ETHIBLOC (Ethicon, Norderstedt, Germany) injection is also performed under CT guidance and anesthesia.]. Selective arterial embolization has been used since the 1980s. Radiotherapy has been used in the past but is contraindicated because of the risk of sarcoma induction.
Recurrence usually occurs after the first year of surgery. Therefore, patients should be monitored on a regular basis for up to 5 years.
FURTHER READING:
Topouchian V, Mazda K, Hamze B et-al. Aneurysmal bone cysts in children: complications of fibrosing agent injection. Radiology. 2004;232 (2): 522-6.
Murphey MD, Andrews CL, Flemming DJ et-al. From the archives of the AFIP. Primary tumors of the spine: radiologic pathologic correlation. Radiographics. 1996;16 (5): 1131-58.
Hudson TM. Fluid levels in aneurysmal bone cysts: a CT feature. AJR Am J Roentgenol. 1984;142 (5): 1001-4
