Vol. 114 No. 1 July 2012

Enormous aneurysmal bone cyst of the mandible: case report andradiologic-pathologic correlationGalal Omami, BDS, MSc,a Reji Mathew, BDS, MDS,b Dennis Gianoli, DDS,c and Alan Lurie, DDS, PhD,d

Farmington and New Britain, Connecticut, and Downers Grove, IllinoisUNIVERSITY OF CONNECTICUT, MIDWESTERN UNIVERSITY COLLEGE OF DENTAL MEDICINE-ILLINOIS, AND THEHOSPITAL OF CENTRAL CONNECTICUT

A 33-year-old patient with a huge aneurysmal bone cyst (ABC) was imaged using cone-beam CT, MRI, andangiography. ABC is an uncommon non-neoplastic, expansile lesion of bone. Although common in the appendicular skeletonand spine, only 2% of the lesions occur in the craniofacial skeleton. The plain radiographic features of gnathic ABC mayshow an omni-expansile unilocular or multilocular radiolucency. Fluid-fluid levels have been reported in cysticcompartments of ABCs; however, this feature is not diagnostically specific for ABC. In this article, we present a case of arapidly growing, extraordinarily large ABC of the posterior mandible, with emphasis on comparative imaging features of this

lesion in cone-beam CT, MRI, and carotid angiography. (Oral Surg Oral Med Oral Pathol Oral Radiol 2012;114:e75-e79)

Aneurysmal bone cyst (ABC) is neither an aneurysmnor a true cyst, but it is an uncommon non-neoplastic,expansile lesion of bone. The ABC is defined by theWorld Health Organization as a benign intraosseouslesion, characterized by blood-filled spaces of varyingsize associated with a fibroblastic stroma containingmultinucleated giant cells, osteoid, and woven bone.1 Itcommonly occurs in the appendicular skeleton andspine2; however, only 2% of the lesions occur in thecraniofacial skeleton.3 Most ABCs of jaws occur inadolescents, predominantly those younger than 20. Thelesion is more commonly seen in the mandible thanmaxilla (3:1), more commonly involving the posteriorregion of the mandible. The lesion appears to have aslight predilection for females. The pathogenesis ofABC remains uncertain, although most regard it asreactive to prior trauma or pathology.3 The radio-graphic features of ABC of jaws can vary from uniloc-ular to multilocular expansile radiolucencies. Fluid-fluid levels may occur when substances of differingdensities are contained within a cystic compartment.Fluid-fluid levels have been reported to be associated

aDiplomate, American Board of Oral and Maxillofacial Radiology;Senior Resident, Oral and Maxillofacial Radiology, University ofConnecticut, School of Dental Medicine.bAssistant Professor, Oral and Maxillofacial Radiology, MidwesternUniversity College of Dental Medicine-Illinois (CDMI).cChair, Oral and Maxillofacial Surgery, the Hospital of Central Con-necticut.dChair, Oral and Maxillofacial Radiology, University of Connecticut,School of Dental Medicine.Received for publication Nov 23, 2011; returned for revision Jan 18,2012; accepted for publication Jan 30, 2012.Published by Elsevier Inc.2212-4403/$ - see front matter

http://dx.doi.org/10.1016/j.oooo.2012.01.023

with ABC, demonstrating hemorrhages of different ag-es; however, this feature is not diagnostically specific.4

Surgical resection or curettage is the treatment ofchoice; in the jaws, curettage has higher recurrencerates than does resection.5 In this article, we present acase of a rapidly growing, extraordinarily large ABC ofthe posterior mandible, with emphasis on the imagingfeatures in cone-beam computed tomography (CBCT),magnetic resonance imaging (MRI), and carotid angio-graphic images and their application to treatment plan-ning of such lesions.

CASE REPORTA 33-year-old African American woman was referred to

the Section of Oral and Maxillofacial Radiology at the Uni-versity of Connecticut School of Dental Medicine for CBCTevaluation of an extensive, painless, rapidly growing swellingof the left posterior mandible. The patient reported that thisswelling had been growing over a period of 5 months. Ex-traoral examination revealed a huge swelling involving al-most the entire lower left side of her face and submandibularregion; digital palpation showed firm to hard texture withouttenderness or egg-crackling sign. The overlying skin lookedslightly erythematous. There was no significant weight loss,and patient’s medical history was otherwise noncontributory.Intraoral examination was remarkable only for extensive den-tal caries. On initial panoramic examination, the lesion was solarge that it extended off the image. It showed a faint radio-lucent circular mass with a suggestion of a thinly corticatedborder superimposed over the inferior ramus, posterior body,and submandibular region, with severe destruction of boneinferior to the inferior alveolar canal giving a “cookie bite”appearance (Figure 1).

CBCT imaging showed a well-defined, spheroid, grosslyexpansile, unilocular, low-density lesion arising from thebasal portion of the left ramus and posterior mandibular body,and occupying the left suprahyoid neck. The lesion had

caused ballooning of the medial, lateral, and inferior cortices

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ORAL AND MAXILLOFACIAL RADIOLOGY OOOOe76 Omami et al. July 2012

of the mandible, and extended anteroposteriorly from thelevel of left mandibular second premolar to the anteriorborder of the sternomastoid muscle. Mediolaterally, it ex-tended laterally, creating discernible facial swelling, and me-dially to encroach on the lateral pharyngeal wall, causingslight airway shift toward the right side. Superoinferiorly, thelesion extended from the level of the coronoid notch ofmandible inferiorly to the superior border of thyroid cartilage.The overall estimated dimensions were 67 � 72 � 75 mm.The lesion appeared to have destroyed, but not displaced, thefloor of the inferior alveolar canal. The expanded corticalmargins, whose cortication was intermittently effaced over alarge portion of the periphery, were markedly undulating withnumerous small indentations of the periosteal surface, andshort wispy septa emanated from the endosteal surface of thebony covering (Figure 2). The appearance of this lesionsuggested a locally destructive lesion of nonodontogenic or-igin and, subsequently, differential diagnosis was limited toABC and central giant cell granuloma.

MRI was performed 4 weeks following the CBCT scan tobetter define the internal contents of this lesion. Pre- andpostcontrast axial and coronal T1-weighted sequences, aswell as coronal, axial, and sagittal T2-weighted sequences,showed a 9-cm, expansile, spheroidal, multiloculated mass,arising from the left mandibular angle, with bony destructionand displacement of superficial soft tissues. The lesion con-sisted of mixed signal-intensity cystic compartments sepa-rated by low T1-signal septae, with a peripheral hypointenserim corresponding to the thin bony shell. There were fluid-fluid levels within the cystic compartments (Figure 3). Post-gadolinium T1 images demonstrated contrast enhancement ofseptae (Figure 4). The differential was more directed towardaneurysmal bone cyst with remote possibilities of giant celltumor (osteoclastoma) and telangiectatic osteosarcoma.

Left internal carotid angiography was performed 5 weeksfollowing MRI scan to identify principal feeder vessels andenable a more precise surgical treatment plan. The angiogramdemonstrated no evidence of tumor enhancement or otherabnormality. The inferior alveolar (mandibular) branch of theleft internal maxillary artery was the predominant tumorfeeder vessel, and therefore it was embolized so as to mini-mize blood loss during surgery (Figure 5). The patient wasoperated on the day following embolization; an immediate

Fig. 1. Panoramic radiograph showing radiolucent lesioncausing destruction of left mandibular angle.

preoperative needle aspiration revealed fresh blood. The le-

sion was surgically approached via a submandibular incisionwith retromandibular extension, and was excised by enucle-ation with preservation of the inferior alveolar nerve. Areconstruction plate was fixed across the surgical defect tosimulate the contour of inferior border of mandible and re-duce the risk of fracture. The 2-week postoperative periodwas uneventful.

Microscopic analysis revealed numerous large, blood-filled, cavernous cystlike spaces throughout; foci of multinu-

Fig. 2. A, Axial CBCT image shows expansile low-densitylesion of posterior left mandible. Note the scalloping patternof the uninterrupted smooth cortex. B, Volume-renderedCBCT scan of skull in anterolateral projection demonstrates3D nature of the lesion.

cleated giant cells and intravascular emboli; and osteoid and

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woven bone trabeculae among stromal elements (Figure 6).The pathology report confirmed the diagnosis of aneurysmalbone cyst.

DISCUSSIONBernier and Bhaskar first reported an ABC involvingthe craniofacial skeleton in 19586; to date, our searchrevealed a total of 121 cases of craniomaxillofacialABC in the English literature.4,7-9 The pathogenesisof ABC is controversial, and theories include trauma,reactive vascular malformation, secondary phenomena,and genetic predisposition.10 The development of ABCfollowing bone fracture or trauma could give credenceto the traumatic etiology of this lesion; however, there

Fig. 3. Axial (A) and sagittal (B) T2-weighted MR imagesfluid-fluid levels (arrowheads) in the ABC.

Fig. 4. Coronal pre- (A) and postgadolinium (B) T1-weighintercystic septae.

are arguments against this proposal, particularly the

fact that often it is difficult to establish a history oftrauma. Kransdort et al. suggested that ABC may resultfrom a vascular disturbance in the form of suddenvenous occlusion or the development of an arterio-venous shunt.2 This would usually occur, if ever itdoes, in more vascular, immature parts of the skeleton.ABC can occur as a secondary phenomenon arising ina preexisting bone lesion, such as solitary bone cyst,osteoclastoma, osteosarcoma, ossifying fibroma, fi-brous dysplasia, osteoblastoma, hemangioendotheli-oma, and hemangioma.11,12 The radiographic featuresof ABC are not characteristic, and, therefore, radiolog-ical differentiation from other expansile jaw lesions

nstrate hyperintense multicystic appearance with numerous

R images of the ABC. Note the contrast enhancement of

demo

ted M

may be difficult.

ORAL AND MAXILLOFACIAL RADIOLOGY OOOOe78 Omami et al. July 2012

The plain radiographic features of ABC of the jawmay show a unilocular or multilocular radiolucencycausing expansion, perforation, and/or destruction ofthe bony cortices.2,13 These features are not diagnosti-cally specific. CT is superior to plain radiography indelineating the thin cortex of new subperiosteal bonesurrounding the lesion.1 Fluid-fluid levels may occurwhenever substances of differing densities are con-tained within a cystic compartment. The levels aredepicted when imaging is performed in a gravity-de-pendent plane as layers of different fluid densities.

Fig. 5. Left common carotid angiogram in lateral projection.Note the inferior alveolar artery feeding the lesion (arrow).

Fig. 6. Photomicrograph showing blood-filled spaces in fi-brous stoma containing abundant multinucleated giant cellsand osteoid. Arrow indicates a blood vessel showing PVAembolization (hematoxylin-eosin stain, magnification �20).PVA, polyvinyl alcohol.

Layering is seen well on CT and MRI because of the

high contrast resolution. Of the 2 modalities, MRIshould be more sensitive than CT in detection of fluid-fluid levels, as it has the advantage in both tissuecontrast and hemorrhage sensitivity. In MRI, the by-products resulting from hemoglobin degradation havediffering signal characteristics.14 The iron atoms ofhemoglobin have a different magnetic effect, depend-ing on the physical and oxidative state of the hemoglo-bin itself.15 Using a 1.5-Tesla MR unit, hyperacute(fresh) oxygenated blood (hemorrhage no more than afew hours old) has approximately the same MR imag-ing characteristics as water, being hypointense on T1-weighted and hyperintense on T2-weighted images.Acute and subacute hemorrhages (1-7 days old), be-cause of the paramagnetic effect of deoxyhemoglobin,have a low signal on T1- and T2-weighted images.Chronic hemorrhage (older than 7 days), with progres-sive oxidation of deoxyhemoglobin to methemoglobin,becomes hyperintense on T1-weighted images. The sig-nal on T2-weighted MRI remains low if the methemo-globin is still intracellular (i.e., if oxidation occurredbefore erythrocyte lysis), therefore having limited mo-tion; however, T2 signal is high when the methemo-globin has become extracellular.15 In summary, thesedimentation effect of stagnant blood is responsiblefor the appearance of fluid-fluid levels on CT and MRimaging, with the top fluid layer consisting of bloodserum and the bottom fluid layer consisting of precip-itated blood cells. The top layer is hypoattenuating onCT scans, isointense to muscle on T1-weighted MRimages, and markedly hyperintense on T2-weightedMR images. The bottom layer is hyperattenuating onCT scans, slightly hyperintense to muscle on T1-weighted MR images, and slightly hyperintense onT2-weighted MR images16 (Figure 3). Fluid-fluid lev-els have been reported as being strongly suggestive ofABC on MRI or CT and have suggested the diagnosisof this lesion.17,18 Fluid-fluid levels also have beenobserved in other lesions, however, such as telangiec-tatic osteosarcoma, osteoclastoma, and chondroblas-toma.17,19 CT appearance of fluid-fluid levels in bonehas also been reported in osteomyelitis and simple bonecyst.20,21 Therefore, fluid-fluid levels are not specific toABC and should not be considered diagnostic of anyparticular lesion. Angiograms have been reported tocharacteristically show arterial branches to the lesion.22

ABC is divided into 3 forms based on microscopicappearances: (1) the vascular “classic” form showsfibrous connective stroma with immature fibroblastsand abundant multinucleated giant cells between nu-merous blood-filled sinuses that may show signs ofthrombosis; (2) the solid variant is characterized byeither inconspicuous vascularity or small vascular

spaces lined by cellular fibrous tissue with osteoid

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formation and foci of calcifying fibromyxoid tissue;and (3) the mixed variant demonstrates features of boththe vascular and solid types, possibly representing atransitional phase of the lesion.23

Selective arterial embolization or injection of scle-rosing agents may contribute considerably in the man-agement of ABC.24 Broadly speaking, surgical curet-tage is recommended as the treatment of choice andhemorrhage in fact is not an operative premonition.25

Conversely, marginal or en bloc resection preferentiallyshould be adopted in recurrent lesions10; however, cu-rettage appears to have a somewhat higher recurrencerate (20%-38%) than does resection (11%-25%).5

Overall, despite recurrences, the long-term prognosisappears favorable.

In conclusion, although fluid-fluid levels are stronglysuggestive of ABC, they are nonspecific, as they havebeen associated with other bone lesions, including tel-angiectatic osteosarcoma, osteoclastoma, and chondro-blastoma. Multimodality imaging may greatly aid in thespecific treatment planning of such lesions, especiallywhen they are of great size.

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2. Kransdorf MJ, Sweet DE. Aneurysmal bone cyst: concept, con-troversy, clinical presentation, and imaging. AJR Am J Roent-genol 1995;164:573-80.

3. Kalantar Motamedi MH. Aneurysmal bone cysts of the jaws:clinicopathological features, radiographic evaluation and treat-ment analysis of 17 cases. J Craniomaxillofac Surg 1998;26:56-62.

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18. Asaumi J, Konouchi H, Hisatomi M, Matsuzaki H, Shigehara H,Honda Y, Kishi K. MR features of aneurysmal bone cyst of themandible and characteristics distinguishing it from other lesions.Eur J Radiol 2003;45:108-12.

19. Matsuura S, Tahara T, Ro T, Masumi T, Kasuya H, Yokota T.Aneurysmal bone cyst of the coronoid process of the mandible.Dentomaxillofac Radiol 1999;28:324-6.

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23. Kershisnik M, Batsakis JG. Aneurysmal bone cysts of the jaws.Ann Otol Rhinol Laryngol 1994;103:164-5.

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Reprint requests:

Galal Omami, BDS, MScSenior ResidentOral and Maxillofacial RadiologyUniversity of Connecticut, School of Dental Medicine263 Farmington AvenueFarmington, CT 06030

jellodent@yahoo.com