AJR 2004; 182:740
© American Roentgen Ray Society
Radiologic-Pathologic Conference of Wilford Hall Medical
Center |
Cortical Aneurysmal Bone Cyst of the Tibia
T. J. Barrett1,2,
Douglas P. Beall1,
Justin Q. Ly1 and
Steven W. Davis3
1 Department of Radiology, Wilford Hall Medical Center, 2200 Bergquist Dr., Ste.
1, San Antonio, TX 78236-5300.
2 Present address: Department of Radiology, Brooke Army Medical Center, 3851
Roger Brooke Dr., Fort Sam Houston, TX 78234-6200.
3 Department of Pathology, Wilford Hall Medical Center, San Antonio, TX
78236-5300.
Received January 13, 2003;
accepted after revision March 4, 2003.
Address correspondence to J. Q. Ly.
The opinions and assertions contained herein are those of the authors and
should not be construed as official or as representing the opinions of the
Department of the Air Force or the Department of Defense.
A21-year-old man presented with a 6-month history of a mass increasing in
size over the right distal tibia. Conventional radiographs showed a 2.0
x 1.5 cm eccentric lytic lesion localized to and expanding the involved
cortical bone (Fig. 1A). CT
revealed an aggressive-appearing cortical lesion protruding medially and
causing marked thinning of the posterior tibial cortex
(Fig. 1B). MRI showed a
multiloculated mass with markedly irregular peripheral margins and several
intratumoral fluid–fluid levels within variably sized cystic spaces
(Fig. 1C). Microscopic
evaluation of the surgically removed mass showed fibroblastic proliferation,
abundant giant cells, focal osteoid deposition, and a large blood-filled space
without an endothelial lining (Fig.
1D). The final diagnosis was cortical aneurysmal bone cyst.
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Fig. 1A. —21-year-old man with cortically based aneurysmal bone cyst of
tibia. Lateral radiograph of right tibia shows expansile, radiolucent
elliptically shaped mass (arrowheads) that involves mid posterior
cortex.
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Fig. 1B. —21-year-old man with cortically based aneurysmal bone cyst of
tibia. Axial CT image through lytic lesion shows its confinement to
posteromedial tibial cortex. Note heterogeneous attenuation of lesion and
markedly thinned but intact cortex.
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Fig. 1C. —21-year-old man with cortically based aneurysmal bone cyst of
tibia. Sagittal fat-suppressed fast spin-echo T2-weighted image shows
multiloculated cystic mass with several fluid–fluid levels
(arrowheads) consistent with hemorrhage into several of numerous
cystic spaces that compose this expansile mass. Tumor is well defined and
lacks surrounding soft-tissue edema.
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Fig. 1D. —21-year-old man with cortically based aneurysmal bone cyst of
tibia. Photomicrograph of surgical specimen shows fibroblastic proliferation,
abundant giant cells, focal osteoid deposition, and large blood-filled space
without endothelial lining; these findings support diagnosis of aneurysmal
bone cyst. Lack of cellular atypia, mitotic figures, or lacy-appearing
osteoids argues against malignant process. (H and E, x40)
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The pathogenesis of aneurysmal bone cysts is uncertain, but aneurysmal bone
cysts are believed to represent a reaction to a localized arteriovenous
malformation [1]. These benign
expansile cystic tumors are known to occur concurrently with other pathologic
entities including giant cell tumors, fibrous dysplasia, chondroblastomas, and
hemangiomas [2]. The
microscopic appearance of the aneurysmal bone cysts is variable
[1]. The essential histologic
features include multiple blood-filled cavernous channels but lacking the
smooth muscle walls and endothelial lining of normal vasculature
[1,
2]. The areas of osteoid
formation may occasionally be surrounded by immature chondroid matrix
analogous to that seen in fibrous dysplasia. Mitotic figures may be numerous
in the area of osteoid formation. Despite the high mitotic rate, the stromal
cells lack anaplastic features, and atypical mitotic figures are absent.
Most aneurysmal bone cysts arise from the diaphyses of long bones, but
other less common sites of occurrence include the vertebrae and short bones of
the hands and feet [2].
Aneurysmal bone cysts may arise from the medullary space, subperiosteal
region, or cortex, as is shown in this case. They tend to occur in patients in
the first two decades of life.
Radiographic findings include an expansile, eccentric osteolytic lesion
involving the metaphysis of long bones or the intramedullary region if
involving the epiphysis. Although benign in nature, aneurysmal bone cysts can
have an aggressive appearance and may be associated with marked cortical
thinning or erosion and periostitis that often occurs at the diaphyseal aspect
of involvement. CT may show interrupted cortex that is often not readily
detected on radiography. MRI will typically show a well-circumscribed,
macrolobulated cystic lesion, often containing multiple fluid–fluid
levels, which correlate with the histologic finding of large blood-filled
spaces without endothelial lining. The finding of fluid–fluid levels is
nonspecific, however, and can be seen with other osseous lesions including
fibrous dysplasia, simple bone cysts, and chondroblastomas
[1,
3,
4].
The treatment for aneurysmal bone cysts is surgical excision with grafting
of the defect and possible radiation therapy and cryotherapy
[3]. Because curettage is
associated with rapid reoccurrence, it is no longer frequently used.
References
- Kransdorf MJ, Sweet DE. Aneurysmal bone cyst: concept, controversy,
clinical presentation, and imaging. AJR1995; 164:573
–580[Abstract/Free Full Text]
- Martinez V, Sissons HA. Aneurysmal bone cyst: a review of 123 cases
including primary lesions and those secondary to other bone pathology.
Cancer 1988;61:2291
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- Woertler K, Brinkschmidt C. Imaging features of subperiosteal
aneurysmal bone cysts. Acta Radiol2002; 43:336
–339[Medline]
- Tsai JC, Dalinka MK, Fallon MD, Zlatkin MB, Kressel HY.
Fluid–fluid level: a nonspecific finding in tumors of bone and soft
tissue. Radiology1990; 175:779
–782[Abstract/Free Full Text]
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