C A S E R E P O R T
Aneurysmal bone cyst of the zygomatic bone
L.K. Surej Kumar & P. Varun Menon
Department of Oral and Maxillofacial Surgery, Kerala Institute of Medical Sciences (KIMS), Trivandrum, Kerala, India
Key words:
aneurysmal bone cyst, maxillofacial region, rare, zygoma
Correspondence to LK Surej Kumar
Department of Oral and Maxillofacial Surgery Kerala Institute of medical sciences (KIMS) P.B.No.1, Anayara P.O
Trivandrum 695029 Kerala
India
Tel.: +919447032516 Fax: +91-472-258 7874 Email: surejkumarlk@gmail.com Accepted: 23 February 2016 doi:10.1111/ors.12215
Abstract
Aneurysmal bone cyst (ABC) is a rare haemorrhagic, non-neoplastic lesion, most commonly seen involving the long bone and spine. It is characterised by its expansile nature, high vascularity and multi-cystic appearance. It is a rare lesion in the maxillofacial region with its occurrence more in the mandible than in the maxilla. So far only four cases of ABC in the zygoma have ever been reported in the English literature. Here we report a rare case of ABC of zygomatic bone with a short review.
Introduction
Aneurysmal bone cyst (ABC) is a benign, non- neoplastic lesion of the bone, characterised by replacement with fibro-osseous tissue containing blood-filled sinusoidal or cavernous spaces. It is com- monly found in the long bones and spine, and its inci- dence in the maxillofacial region is rare and the mandible is often affected more than the maxilla. So far it has been found that only four cases of ABC of zygoma have been reported till date1. Though the aetiopathogenesis still remains a mystery, various authors have proposed different theories for the same.
The characteristic signs of ABC include sudden growth and bi-cortical expansion with a cystic appearance.
The rapid destruction of the bone and cystic changes often mislead the clinicians in terms of malignancy.
Case report
A 63-year-old male came to oral and maxillofacial department with a complaint of a swelling on right cheek region since 3 months (Fig. 1) and had visited various centres for the same. He had been under
intravenous antibiotics for the same from different centres and also had undergone extraction of the maxillary teeth for the same. No history of trauma was elicited.
Clinical examination revealed a large swelling extending from infraorbital margins to the anterior wall of maxilla and laterally to the zygomatic arch.
Skin over the swelling was smooth without punctum and non-adhered. Fine-needle aspiration cytology (FNAC) was done extraorally and dark coloured blood was the aspirate. Computed tomography revealed bicortical expansion of a zygoma with the probability of an expansile osteolytic lesion involving right zygomatic bone with a cystic space (Fig. 2).
Correlating CT findings, clinical findings and aspi- rate, a provisional diagnosis of ABC was made. An interesting observation was that, one week post- operatively a sinus formation was seen at the FNAC site. Surgical excision of the lesion was planned under General anesthesia (GA).
An extraoral approach was decided to facilitate the excision of the orocutaneous fistula along with the lesion. Through a standard Webber–Fergusson inci- sion, extraoral sinus was marked along with the
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Weber–Fergusson incision, and flap was raised.
Intraoperative cortical plate over the sinus tract was seen thinned out (Fig. 3), the outer cortical plate was removed and the inner cortical plate was smoothened with a vulcanite bur till a smooth bony surface was obtained (Fig. 4). Local advancement flap from cheek was taken and closure was done pri- marily (Fig. 5). Post-operative phase was uneventful (Fig. 6).
Discussion
In spite of a descriptive history for more than 70 years since the first ABC was described, the clini- cal nature, behaviour, aetiology and treatment still remains a surgical dilemma. An ABC is an expansile, often multilocular, osteolytic lesion, with blood-filled spaces separated by fibrous septa containing giant
cells and reactive bone2. Jaffe and Lichtenstein3first described it as a distinct pathological entity and gave its definition. The term aneurysmal is in fact related to an expansion or distension and cyst usually repre- sent the blood-filled cavity4,5.
The ABC is usually seen occurring in the initial two decades of life and accounts for 1–2% of all pri- mary bone tumours6. It is commonly seen in long bones and vertebrae and rarely seen in jaws, and the mandible is affected twice as frequently as the max- illa7–9. Another study has also shown the mandible to be more involved than the maxilla in a ratio of 55% to 45%. Both males and females were equally affected without sex predilection8,9. The rarest of the site for occurrence is the zygomatic bone with only four cases so far been reported till date1.
The aetiology of the ABC is still uncertain and var- ious theories have been proposed. According to Lichtenstein3, a change in local haemodynamics per- haps following thrombosis of a sizeable vein or an anomalous arterio-venous communication may have resulted in the formation of ABC. As there was no evidence of muscular tissue in the vascular channel, Lichenstein theory was discarded. Some authors10 suggested complex connective tissue replacement of a canalised haematoma of bone marrow. They pro- posed that if the circulatory connections are main- tained by haematoma with damaged vessels, then an ABC develops and on the other hand, if this connec- tion is blocked then a giant-cell granuloma is formed. They also suggested it as a false aneurysm as blood was seen circulating through it10. No further advancement in the aetiology has taken place since then.
Clinically, ABC presents as an asymptomatic lesion that may grow rapidly in time, resulting in
A B
Figure 2 Axial and coronal CT images.
Figure 1 Pre-operative clinical picture.
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Surej Kumar & Varun Menon Aneurysmal bone cyst
expansion and destruction of the surrounding bone structure; subsequent invasion of the cortical bone and compression on adjacent nerve, soft tissue or joint inevitably results in pain1,7,8.
Definite diagnostic criteria of an ABC have yet to be established in spite of more than half a century since its first presentation. Radiographic findings are suggestive, but not definitive, in diagnosing the lesion. The imaging studies, even CT, does not pro- vide a clear diagnosis and ABC may be added to other list of differential diagnosis like venous malformation of the bone, ameloblastoma, central
giant-cell granuloma, myxoma, intraosseous hae- mangioma, chondroblastoma and osteoblastoma10. Normally, they present as cortical expansion with radiolucent or mixed variant giving a cystic appear- ance. CT is usually helpful in knowing the extent of the lesion rather than knowing the diagnosis11.
Aspiration is considered as one of the diagnostic techniques, but our experience though with single case aspiration can result in formation of orocuta- neous fistula, so aspiration should be preferentially avoided or postponed unless immediate surgery is planned.
Figure 4 Intraoperative picture after smoothening the bony surfaces.
Figure 5 Closure of surgical site.
Figure 6 Follow-up post-operative picture.
Figure 3 Standard incision placed and flap raised.
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Aneurysmal bone cyst Surej Kumar & Varun Menon
Various treatment modalities available for ABCs include: simple curettage, complete excision, radia- tion therapy, embolisation or a combination of these methods12. Sometimes these lesions especially in lower limbs are very aggressive12 and are trea- ted by amputation or excision. No such aggressive lesions have been reported in head and neck region, so curettage of the lesion has been advo- cated. We too advocated curettage with exception that in our case the overlying was excised as the aspiration had resulted in orocutaneous fistula for- mation.
A relatively high recurrence rate of 10–20% is seen in case of ABCs; however, recurrence is usually rare when the tumour is completely removed12. There is not much of known recurrence rate reported for cases in head and neck region and occurrence of ABC in zygoma even rarer as only four cases has been reported till date1, and regular follow-up has to be maintained to evaluate the recurrence.
Conclusion
Although science is so advanced, no protocol has been established for proper diagnosis and treatment of ABC. Its aetiopathogenesis as well as its diagnostic and treatment dilemma continues. Perhaps research still going on in these various aspects will probably bring in new dimensions in the treatment of ABC in future.
Conflict of Interest
The authors confirm that there are no conflicts of interest.
Ethical Approval
None required.
References
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