C A S E R E P O R Tors_1146 45..48
The peripheral adenomatoid odontogenic tumour: a case report
L.M. Bowers1, D.M. Cohen1,2, A. Fetner2& I. Bhattacharyya1
1Department of Oral and Maxillofacial Diagnostic Sciences, Division of Oral Pathology, University of Florida College of Dentistry, Gainesville, FL, USA
2Department of Periodontology, University of Florida College of Dentistry, Gainesville, FL, USA
Abstract
An 11-year-old male presented with a localised erythematous gingival enlargement of the anterior maxillary gingiva and an associated deep facial pocket. Biopsy specimens were obtained. Histopathological examination of the submitted tissue showed a cystic lining consisting of proliferating odontogenic epithelium with spindle-shaped cells forming small ductules and well-formed duct-like structures lined by pseudo-stratified columnar epithelium. A diagnosis of peripheral adenomatoid odontogenic tumour (PAOT) was rendered. The PAOT is a rare entity that can present as an erythematous gingival swelling, similar to an epulis or fibroma. Dentists should be aware that unusual pathological entities can have a variety of presentations and that definitive diagnosis may require submission of tissue for histopathological examination.
Key words:
adenomatoid tumour, gingival peripheral tumor, odontogenic tumour, pathology
Correspondence to:
I Bhattacharyya
Department of Oral and Maxillofacial Diagnostic Sciences
Division of Oral Pathology
University of Florida College of Dentistry 1600 SW Archer Road
PO Box 100414 Gainesville FL 32610 USA
Tel.:+1 352 273 6689 Fax:+1 352 392 2507
email: [email protected]fl.edu Accepted: 23 November 2011 doi:10.1111/j.1752-248X.2011.01146.x
Introduction
The adenomatoid odontogenic tumour (AOT) is a benign lesion of odontogenic origin. The AOT appears in three clinical variants: a follicular type, an extra- follicular type and a peripheral type1,2. Peripheral odontogenic tumours are defined as tumours that demonstrate the histological characteristics of their intraosseous counterparts but occur exclusively in the soft tissue2. We report a rare case of peripheral adenomatoid odontogenic tumour (PAOT) occurring in the anterior maxillary gingiva of an 11-year-old male who presented with an erythematous gingival swelling of 1 year’s duration. We briefly review the literature regarding the prevalence, histopathological features and treatment of this unusual entity.
Case report
An 11-year-old male presented (to AF) for evaluation of a ‘red marginal lesion’ of 1 year’s duration. Six months prior to the evaluation, the lesion was deter-
mined to be not plaque-related and was removed by a paediatric dentist using electrosurgery (no specimen was obtained). The lesion returned 6 months later, and the patient was referred for further evaluation to AF.
Upon examination, a firm erythematous, raised lesion was noted on the facial gingiva associated with the permanent maxillary left central incisor (Fig. 1). A normal radiographic presentation was noted. On the basis of the clinical and radiographic findings, the dif- ferential diagnosis included an epulis and a pyogenic granuloma. A surgical flap was raised, and the tissue along with the associated gingiva was removed. It was noted that the lesion was attached to the facial flap and was not associated directly with the tooth. Facial bone expansion was observed relative to the adjacent teeth.
No bony perforation was noted, but there was 7 mm of root exposed from the mesiofacial to the distofacial line angles of the permanent maxillary left central incisor.
The specimen was placed in a 10% formalin solution and sent for microscopic examination.
Histological examination of the soft-tissue spe- cimen revealed an encapsulated lesion containing
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proliferating cystic odontogenic epithelium, well- formed ductal structures (Fig. 2) and scattered small calcospheritic masses (Fig. 3). In the specimen taken from between the teeth and the bony defect, additional cystic odontogenic epithelium of a similar appearance was seen. The histological findings were consistent with a well-encapsulated PAOT.
The patient was seen for follow-up at 1 week and 6 weeks after biopsy. Healing was uneventful. Post- operative radiographs of the area did not show any associated pathology. The tissue appeared completely healed at 6 weeks, and the probing depths had returned to clinically normal readings (Fig. 4). No further recurrence has been reported to date.
Discussion
The AOT was proposed as a distinct entity by Stafne in 1948 when he described three cases in which the epi-
thelial components formed duct-like structures. The World Health Organization (WHO) in 1971 adopted the term proposed by Philipsen and Birn as ‘adenoma- toid odontogenic tumour’ and defined the lesion as, ‘A tumour of odontogenic epithelium with duct-like structures and with varying degrees of inductive change in the connective tissue’3. In 2005, the WHO redefined the AOT as ‘composed of odontogenic epi- thelium in a variety of histoarchitechtural patterns, embedded in a mature connective tissue stroma char- acterized by slow but progressive growth’4.
The peripheral variant comprises between 2.3% and 4.5% of all cases of AOT5–7; the lowest frequency of the three AOT types6. Similarly to all variants of AOT, the PAOT shows a distinct male: female ratio ranging from 1:2 to 1:145,7,8. The peak incidence of the PAOT is in the second decade, with a reported mean age at presenta-
Figure 1 Preoperative appearance of erythematous gingival lesion asso- ciated with the permanent maxillary left central incisor.
Figure 2 Proliferating cystic odontogenic epithelium with well-formed ductal structures (haematoxylin and eosin; original magnification¥ 200).
Figure 3 Calcospheritic masses distributed in the connective tissue stroma (haematoxylin and eosin; original magnification¥ 200).
Figure 4 Six weeks post-operatively, showing no recurrent lesion and return of clinically normal probing depths.
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tion ranging from 11.9 to 14 years5,7; the lowest mean age for any AOT variant6. The peripheral lesions are most commonly seen in the anterior maxilla, most fre- quently in the incisor or canine region, but have also been reported in the anterior mandible2. The PAOT is the only peripheral odontogenic tumour that shares the age, gender and site predilections of its central counterpart5,9. A review of 48 well-documented cases of peripheral epithelial odontogenic tumours showed that the PAOT accounted for 12.5% of the cases2. In 2006, a review of 45 cases of peripheral odontogenic tumours collected over a 20 year period from a large biopsy service revealed no cases of PAOT10.
The clinical appearance of the PAOT is that of a painless, slow-growing gingival swelling. One reported case produced protrusion of the associated teeth2,11. The duration of the lesion may vary from months to years2. Preoperative differential diagnoses may include fibroma, gingival hyperplasia or epulis2, pyogenic granuloma, peripheral ossifying fibroma, peripheral giant cell fibroma or other peripheral odontogenic tumour. As in this case, a bony defect may be associated with the lesion. Radiographic appearance may vary from normal to demonstrating evidence of superficial erosion of the underlying bone2,8,12,13.
The histological features of the AOT involve cuboidal or columnar cells of odontogenic epithelium forming nests or rosette-like structures with minimal inter- vening fibrous connective tissue stroma. Within the rosette-like structures, eosinophilic amorphous mate- rial is often seen. Tubular or duct-like structures are typically present within the cellular areas. These struc- tures are lined by simple columnar epithelial cells with the nuclei polarised away from the luminal space. The lumen may contain an eosinophilic material, cellular debris or may be without contents. In addition to forming the duct-like structures, the cuboidal to columnar cells may form convoluted cords in compli- cated patterns that often show invaginations. The con- nective tissue stroma of the AOT is loosely arranged and contains dilated, thin-walled congested vessels4.
Dystrophic calcification, believed to be dentinoid or cementum in nature14, of varying amounts and pat- terns, is often seen within the lumina of the duct-like structures, scattered among the epithelial components or in the stroma of the AOT8,12,13. The number, size and degree of calcifications present will influence the radiographic appearance of the lesion15.
The histology of the tumour does not differ widely;
the histological appearance of all variants (follicular, extra-follicular and peripheral) is identical and shows remarkable consistency16,17. The PAOT, like the intraosseous lesion, is usually solid, however, in this
case, the lesion had a cystic component. Unlike the intraosseous lesion, PAOTs are generally unencapsu- lated, although these lesions have also been reported as surrounded by a relatively thick capsule2, as was observed in this case.
The PAOT has been proposed to be an erupted AOT;
as normal eruption progresses, the tooth pushes an intraosseous or gingival hamartomatous growth peripherally2. There are reports of cases in which an unerupted tooth associated with an AOT was orth- odontically guided into the arch prior to excision. It was noted that the AOT accompanied the repositioned tooth to the gingiva5. This is in agreement with the lesion seen in this case, as it had both peripheral and central components.
The AOT, in general, is rarely detected radiographi- cally, but there may be underlying erosion of the bony cortex8,12,13. The presence or absence of a moat-like osseous defect may depend on the initial position of AOT; namely, superficial small AOT of the follicular type may present as an entirely soft-tissue process post-eruption. The unique alveolar bone alterations are thought to most likely represent the remaining erup- tive path of the AOT rather than the result of pressure fenestration by the PAOT5.
Treatment of the PAOT involves conservative surgi- cal excision and evaluation and appropriate treatment of an underlying bony defect if present. There have been no reports of recurrence of this lesion2. We speculate that incomplete excision of the original lesion occurred, resulting in its apparent recurrence in this case. Because of the obvious encapsulation of the lesion and histopathological and clinical evidence of complete excision in this case, recurrence is not expected.
Conclusion
In conclusion, we report a rare case of a PAOT in an 11-year-old male which presented as a recurrent erythematous gingival swelling with a deep periodon- tal pocket associated with the permanent maxillary left central incisor. The PAOT is the rare variant of the AOT which, histologically, is composed of cuboidal or columnar cells of odontogenic epithelium forming nests or rosette-like structures, duct-like structures and may have dystrophic calcifications. An underlying bony defect or saucerisation of the involved bone may be present. This case illustrates the necessity of sub- mission of all specimens removed from the oral mucosa for histopathological examination. Treatment consists of conservative surgical excision with minimal likeli- hood of recurrence.
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It is important for dentists and specialists to recognise that pathological entities can have a variety of clinical presentations. When an appropriate course of action may be in question regarding a pathological lesion, referral to a specialist and submission of tissue for microscopic examination may be necessary.
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