AJR 2004; 182:130
© American Roentgen Ray Society
Radiologic-Pathologic Conference of Wilford Hall Medical
Center |
Calcaneal Chondroblastoma with Secondary Aneurysmal Bone Cyst
Justin Q. Ly1,
Lorine M. LaGatta2 and
Douglas P. Beall1,3
1 Department of Radiology, Wilford Hall Medical Center, 2200 Bergquist Dr., Ste.
1, Lackland AFB, TX 78236-5300.
2 Department of Pathology, Wilford Hall Medical Center, San Antonio, TX
78236-5300.
3 Department of Radiology, Uniformed Services University of the Health Sciences,
4301 Jones Bridge Rd., Bethesda, MD 20814-4799.
Received September 23, 2002;
accepted after revision February 24, 2003.
Address correspondence to J. Q. Ly
(jly15544{at}hotmail.com).
The opinions and assertions contained herein are the private views of the
authors and are not to be construed as official or as representing the views
of the Department of the Air Force or the Department of Defense.
A 25-year-old man presented with increasing ankle pain. Physical
examination was unrevealing. Ankle radiography showed a large osteolytic
lesion expanding the calcaneus (Fig.
1A,
1B,
1C,
1D). Diffuse calcaneal cortical
thinning was evident, but cortical disruption and adjacent soft-tissue
involvement were not. The calcaneal tumor contained numerous thick septa,
areas of hazy matrix with peripheral scattered lytic components. MRI results
were remarkable for several fluid–fluid levels in relatively large
cystic spaces, a finding that can be seen with giant cell tumor, aneurysmal
bone cyst, or chondroblastoma. The patient underwent curettage and bone
packing. Gross examination of the surgical specimen showed multiple fragments
of tan and white soft tissue associated with clotted blood and numerous bone
fragments; the soft-tissue component revealed multiple cystic spaces, some of
which were filled with blood clots. The final pathologic diagnosis was
chondroblastoma with secondary aneurysmal bone cyst.
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Fig. 1A. —25-year-old man with chondroblastoma and secondary aneurysmal
bone cyst of calcaneus. Lateral radiograph of left ankle shows lytic process
involving entire calcaneus, with endosteal scalloping and large thick internal
septa. Central portion of lesion has hazy appearance with several focal lytic
peripheral areas.
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Fig. 1B. —25-year-old man with chondroblastoma and secondary aneurysmal
bone cyst of calcaneus. Sagittal proton density–weighted image of
calcaneus shows well-delineated mass occupying entire calcaneus and containing
several large thin-walled cystic spaces of varying sizes, several containing
fluid–fluid levels.
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Fig. 1C. —25-year-old man with chondroblastoma and secondary aneurysmal
bone cyst of calcaneus. Lateral skeletal scintigraphic image of foot shows rim
of increased uptake at periphery of calcaneus corresponding to reactive
osteoblastic activity. This area of uptake surrounds relatively photopenic
central portion of calcaneal tumor corresponding to cystic spaces seen on MRI
(B).
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Fig. 1D. —25-year-old man with chondroblastoma and secondary aneurysmal
bone cyst of calcaneus. Photomicrograph of histologic specimen reveals sheets
of chondroblasts, giant cells, and aneurysmal bone cyst formation consistent
with diagnosis of chondroblastoma and concomitant aneurysmal bone cyst
(arrow) of calcaneus. (H and E, x10)
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Aneurysmal bone cysts are benign expansile lesions that can be classified
as primary (65%) or secondary (35%)
[1]. Secondary aneurysmal bone
cysts can arise from preexisting benign or malignant lesions. Most (80%) show
the radiographic characteristics of the preexisting tumor. Many of these
"blowout" lesions (as described by Jaffe
[2]) destroy most of the
underlying process, allowing a missed diagnosis of malignancy at histologic
examination. To prevent misdiagnosis, it is essential that the radiologist
report any atypical and malignant features. Common preexisting tumors include
giant cell tumors, osteoblastomas, and angiomas
[3]. Less common underlying
processes include fibrous dysplasia, chondromyxoid fibroma, unicameral bone
cyst, fibrous histiocytoma, eosinophilic granuloma, radiation osteitis,
osteosarcoma, trauma, and fibrosarcoma
[4]. The typical radiographic
appearance of a primary aneurysmal bone cyst is an eccentric, expanded, and
sometimes destructive osteolytic lesion that may contain internal septa. CT
and MRI often show multiple fluid levels contained within thin-walled vascular
cystic spaces. The fluid levels represent hemorrhage.
Chondroblastomas are rare tumors that occur predominantly in patients less
than 20 years old. They occur almost exclusively in the epiphyses, but may
extend into the diaphyses of long bones. They can be secondarily involved by
an aneurysmal bone cyst in 10–15% of cases
[3]. Secondary involvement of a
chondroblastoma by an aneurysmal bone cyst is more likely in patients older
than 20 years. Early in the process, this phenomenon has the characteristics
of solitary chondroblastoma: a patient less than 20 years old with a
well-defined lytic epiphyseal lesion that shows geographic borders, punctate
calcifications, chondroid matrix, periostitis, and bone marrow edema. The
features of aneurysmal bone cyst appear later, with increasing destruction of
the preexisting elements.
Intralesional fluid–fluid levels are common to both chondroblastomas
and aneurysmal bone cysts and are therefore not generally helpful for
distinguishing the two entities. Histologic examination is required to make
this determination. Histologically, a primary aneurysmal bone cyst shows
blood-filled anastomosing fibrous-walled channels lined completely or
incompletely by endothelial cells. The fibrous walls may contain hemosiderin
deposits, giant cells, RBCs, and spicules of reactive bone
[1]. The secondary aneurysmal
bone cyst usually contains the additional characteristics of the coexisting
lesion.
The treatment for aneurysmal bone cysts and
chondroblastomas—curettage and bone grafting—is similar, which
simplifies patient treatment.
References
- Bonakdarpour A, Levy WM, Aegerter E. Primary and secondary
aneurysmal bone cyst: a radiological study of 75 cases.
Radiology1978; 126:75
–83[Abstract]
- Jaffe HL. Aneurysmal bone cyst. Bull Hosp Joint
Dis 1950;11:3
–13[Medline]
- Mirra JM. Chondroblastoma. In: Mirra JM, Picci P, Gold RH, eds.
Bone tumors. Philadelphia, PA: Lea & Febiger,1989
: 589–623
- Kransdorf MJ, Sweet DE. Aneurysmal bone cyst: concept, controversy,
clinical presentation, and imaging. AJR1995; 164:573
–580[Abstract/Free Full Text]
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