C A S E R E P O R T

Unicystic ameloblastoma mimicking a lateral periodontal cystO.W. Majid

Department of Oral and Maxillofacial Surgery, College of Dentistry, University of Mosul, Mosul, Iraq

Key words:ameloblastoma, cyst, surgery

Correspondence to:Dr OW Majid

Department of Oral and Maxillofacial Surgery

College of Dentistry

University of Mosul

Mosul

Iraq

Tel.: 0964 06 812910

Fax: 0964 06 812900

email: omerw_majid@yahoo.co.uk

Accepted: 14 November 2012

doi:10.1111/ors.12011

Abstract

Unicystic ameloblastoma (UA) is a subtype that represents 5–22% of allameloblastoma types. In this report, a 41-year-old patient is presented witha swelling in the right side of the mouth since 2 months with no facial dis-figurement. On clinical examination, a firm non-tender mass bulgingbetween the right lower first and second premolars. Fine-needle aspirationyielded only little non-specific fluid. A panoramic radiograph was taken,which showed a large well-defined radiolucency measured about 3.5 cm indiameter resembling a lateral periodontal cyst. The lesion was totallyremoved by surgical enucleation under local anaesthesia. The histopatho-logical examination confirmed the diagnosis of UA of mural type. Thepatient was informed of the prognosis and put on periodic follow-up.

Clinical significance

Unicystic ameloblastoma (UA) usually occurs in theposterior mandibular region. This report describes acase of UA that was confined to the lower premolarregion mimicking a lateral periodontal cyst. However,there were some atypical features that may be useful indifferentiating between the two lesions including theage of the patient at presentation, the size of the lesion,and an evident root resorption of adjacent teeth. Suchfeatures would be helpful for professionals to identifyaggressive lesions and provide the appropriate treat-ment. This would also affect the referral patterns tospecialists for more aggressive treatment.

Introduction

UA is a subtype of ameloblastoma that was firstdescribed in 19771. It represents 5–22% of all amelob-lastoma types2. Most of these lesions are discovered bymicroscopic examination of a large unilocular cyst inyoung patients who are 16–20 years of age3. Between50 and 80% of UAs are associated with tooth impac-tion, the mandibular third molar being encountered inthe vast majority of cases with figures ranging from 52to 100%4. Large lesions may cause a painless slowly

growing swelling of the jaws, which may lead tomovement of tooth roots and root resorption5.

Radiographically, the UA is often a well-definedunilocular radiolucency with a scalloped or lobulatedborder that is usually surrounding the crown of theimpacted tooth, as is seen with dentigerous cysts6.Histopathologically, three subtypes were described:luminal, showing a flat ameloblastic cyst lining; intralu-minal, characterised by tumour growth into the cystlumen; and mural, which exhibits infiltrating growthinto the wall of the cyst and possibly beyond into thesurrounding bone4,7. The first two patterns are usuallytreated by enucleation and curettage, while mural UAmay require more radical surgery7,8.

More than 90% of UAs are found in the mandible,usually in the posterior regions. In only rare instances,lesions occur in the premolar area, which is thecommon site of lateral periodontal cyst3. This reportdescribes the management of a case of UA in a41-year-old male that showed similar presentation tolateral periodontal cyst.

Case report

A 41-year-old man presented with painless swellingin the right side of the mouth. The patient said that

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Oral Surgery ISSN 1752-2471

83Oral Surgery 6 (2013) 83–87.

© 2012 John Wiley & Sons A/S. Published by Blackwell Publishing Ltd

swelling was slowly growing over the last 2 months.No facial disfigurement or asymmetry was evident.Intraoral examination revealed a firm bulging mass inthe right alveolar area between the lower premolars(Fig. 1). The overlying mucosa was normal in colourand texture. There was no difficulty in opening themouth, chewing or articulating. On palpation of themass, there was no tenderness. Submandibular andcervical lymph nodes were non-palpable. Electricalpulp testing showed vital teeth in the area except forthe second premolar, which gave a questionableresponse. Medical history indicated that the patientwas otherwise normal with no history of systemicdiseases. Fine-needle aspiration was attempted, butonly little fluid could be obtained. Subsequent his-topathological examination revealed epithelial andchronic inflammatory cells in the specimen. A pano-ramic radiograph was done, which showed a largecystic lesion in the right side of mandible (Fig. 2). The

radiolucency, which was well defined, extended fromthe canine to the first molar and measured about3.5 cm in its largest diameter. Displacement of thepremolars and erosion of roots were evident.

Differential diagnosis at this stage included lateralperiodontal cyst, radicular cyst and odontogenic kera-tocyst. Surgical removal of the lesion under localanaesthesia was planned after discussion with thepatient. After inferior alveolar nerve block and longbuccal nerve infiltration, a three-sided mucoperiostealflap was elevated and the surgical area was adequatelyexposed. Pieces of the thin buccal cortical bone overly-ing the lesion were carefully removed by a small arteryforceps. Then the lining of the lesion was easily sepa-rated from the bone by blunt dissection. After wideningof the buccal window, the lesion was readily removedin toto (Fig. 3). The specimen, measuring about 2 cm indiameter, was preserved in a formalin container andsent for histopathological examination. The sharpedges were trimmed and smoothed, and the resultantcavity was copiously irrigated with an antiseptic solu-tion before suturing the flap back using 3/0 silk suture.Post-operative antibiotics and analgesics were pre-scribed. At suture removal, 7 days later, the woundshowed uneventful healing; however, the premolarsshowed noticeable mobility during examination,which was significantly reduced at the next visit 1month later.

Histopatholgical examination of the surgical speci-men showed a cystic cavity lined by an epitheliumconsisting of palisading columnar basal cells layercovered by loosely arranged stellate reticulum like cells(Fig. 4). In some areas, there were follicles of the lattercells within the connective tissue capsule (Fig. 5). Such

Figure 1 Preoperative view showing a bulging mass between the

premolars.

Figure 2 Panoramic view demonstrates unilocular radiolucency in the

mandible.

Figure 3 Intraoperative view showing the surgical cavity immediately

after enucleation.

Unicystic ameloblastoma: case report Majid

84 Oral Surgery 6 (2013) 83–87.

© 2012 John Wiley & Sons A/S. Published by Blackwell Publishing Ltd

features were consistent with the diagnosis of muralUA. Because this diagnosis carries a risk of recurrence,the patient was informed about the prognosis andlong-term follow-up period was planned. After 7months, there were no clinical or radiographic signs ofrecurrence. Instead, panoramic radiograph of the lastfollow-up visit showed slight reduction in the size ofthe bone defect, with new bone formation at theperiphery (Fig. 6).

Discussion

The current report presents a case of UA that wasdiagnosed by histopathological examination aftercomplete removal of the lesion. Clinically, most fea-tures were consistent with lateral periodontal cyst,

although the lesion size was larger than that in typicalcases. The diagnosis of UA was not considered in theearly management because such lesions are rarelyfound confined to the premolar region, which is theregion where lateral periodontal cyst usually devel-ops3. Most reported cases of UA had some extensionto the molar region and the ramus9. The present caseadds further evidence to what has been reported inthe literature about the likelihood of frequent clinicalmisdiagnosis of such lesions as non-neoplasticcysts10,11.

It is extremely important in the practice to differ-entiate UA from other odontogenic cysts because theformer has a higher rate of recurrence than the latterafter enucleation12. More aggressive treatment, likemarginal resection, may be required for UA, whichcalls for appropriate referrals in such cases. Therefore,differentiation between the two lesions is mandatory.

Lateral periodontal cyst (LPC) is typically locatedlaterally to a root or roots of vital teeth, most often inthe mandibular canine-premolar region5. There is apeak in the prevalence of lateral periodontal cyst in thesixth decade of life5,13. Radiographically, this cystusually presents as unilocular, well-defined, oval orteardrop-shaped radiolucency between the cervicaland apical part of the tooth root, and it is usuallysmaller than 1 cm in diameter13,14. Divergence of theroots may occur, especially with larger cysts, but rootresorption is not seen14,15.

In the present case, three atypical clinical andradiographic features were exhibited in the lesion,which was initially diagnosed as LPC. First, thepatient’s age (41 years) was younger than the age ofpeak incidence for LPC. This age was consistent withthe mean age reported in the literature for ‘no

Figure 4 Histopathological features of unicystic ameloblastoma.

Figure 5 Follicle of ameloblastic cells in the connective tissue stroma

(mural type).

Figure 6 Panoramic radiograph taken 7 months post-operatively.

Majid Unicystic ameloblastoma: case report

85Oral Surgery 6 (2013) 83–87.

© 2012 John Wiley & Sons A/S. Published by Blackwell Publishing Ltd

impaction’ UAs (i.e. have no association with animpacted tooth), which were generally found to occurin patients in the fourth or fifth decade, almost 20years separate the mean age of the impaction-associated variant4,16.

Second, the size of the lesion (3.5 cm in the largestdiameter) was larger than any one previously docu-mented for LPC13,14. The radiolucency extended beyondthe apices of adjacent roots and involved more thantwo teeth. The shape of the lesion was also different,with more horizontal invasion along the body of themandible.

Third, root resorption was evident in the lowerpremolars and first molar, which is not a sign of LPC.This may refer to the aggressiveness of the lesionbecause conventional non-aggressive cystic lesions donot usually induce root resorption unless they reach aremarkable size and cause wide root displacement. Incontrast, the extent of root resorption in our case wasnot directly related to the degree of root displacement,which indicates a higher rate of growth of the lesionand not only due to pressure effect.

The last two features mentioned have already beenconsidered, among others, to be indications for serialsectioning and thorough microscopical examination ofthe surgical specimen taken from any lesion thoughtto be an LPC17. The present report highlights somerelevant features that must be considered duringpre-surgical clinical and radiographic examination.Knowing the differences between pathologies is veryimportant in planning the treatment.

It has been reported that the strongest tendency formural pattern occur in the ‘no impaction’ category ofUA4,18. The presence of a mural component in the his-topathology would change the treatment modality to amore aggressive approach if known before surgery8.This was not possible in our case, so a conservativetreatment was performed, and because the lesion hadbeen completely removed, no further surgery wasplanned. However, considering the high rate of recur-rence of this lesion based on the evidence in the litera-ture19,20, it is essential that long-term follow-up of thepatient be established.

In conclusion, there are some clinical and radio-graphic signs that may be useful to differentiatebetween the two lesions including the age of presen-tation, the size of the lesion, and an evident rootresorption of adjacent teeth. This would be helpfulfor professionals in identifying aggressive lesionsthat may require referral to a maxillofacial specialistfor more aggressive treatment. However, the finaldiagnosis only may be given after histopathologicalexamination.

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Majid Unicystic ameloblastoma: case report

87Oral Surgery 6 (2013) 83–87.

© 2012 John Wiley & Sons A/S. Published by Blackwell Publishing Ltd