Year : 2007 | Volume
: 18 | Issue : 3 | Page : 128--130
Unicystic ameloblastoma with the presence of dentin
B Sivapathasundharam, A Einstein
Department of Oral and Maxillofacial Pathology, Meenakshi Ammal Dental College and Hospital, Chennai, Tamilnadu, India
Department of Oral and Maxillofacial Pathology, Meenakshi Ammal Dental College and Hospital, Chennai, Tamilnadu
We present a case of unicystic ameloblastoma of the posterior mandible in a 28 year-old female, histologically showing luminal and intramural plexiform epithelial proliferation with typical dentin in the connective tissue capsule. The characteristics of hard tissue formation in ameloblastomas reported in existing literature and the possible origin of the dentin mass seen in our case are discussed.
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Sivapathasundharam B, Einstein A. Unicystic ameloblastoma with the presence of dentin.Indian J Dent Res 2007;18:128-130
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Sivapathasundharam B, Einstein A. Unicystic ameloblastoma with the presence of dentin. Indian J Dent Res [serial online] 2007 [cited 2022 Aug 11 ];18:128-130
Available from: https://www.ijdr.in/text.asp?2007/18/3/128/33789
The recent World Health Organisation (WHO) classification of odontogenic tumours, similar to the earlier classification, places ameloblastomas under the category of odontogenic tumours with no inductive potential.  Literature however reveals reports of unusual cases of ameloblastomas, histologically showing the formation of hard tissue such as bone, dentin or dentinoid formation. ,,,,, Histologically, some of these cases have areas resembling adenomatoid odontogenic tumour (AOT) as well. , We herewith report a case of unicystic ameloblastoma with the histological presence of dentin and discuss the possible origin of the hard tissue observed.
A 28 year-old female reported to our outpatient department with a slow-growing swelling of the lower left back tooth region. The swelling was of sudden onset and of two years' duration. The patient gave a history of root canal treatment in the permanent mandibular left second molar tooth three years ago and stated that it had been extracted six months later following complaints of pain and pus discharge.
Examination revealed a diffuse, nontender, smooth-surfaced and hard swelling over the left posterior aspect of the lower jaw. Radiography revealed a large multilocular radiolucency involving the posterior aspect of the mandible, extending from the first premolar region to the angle of mandible [Figure 1]. The radiolucency was closely associated with the roots of teeth 35 and 46. Tooth 38 was displaced to the upper part of the ramus. A provisional diagnosis of odontogenic tumour was made and incisional biopsy was performed.
Sections from the biopsied specimen stained with hematoxylin and eosin revealed a cystic cavity having an ameloblastomatous lining [Figure 2]. There was intramural proliferation of the odontogenic epithelial cells composed of ameloblastomatous tissue of the plexiform type [Figure 3]. One area of the specimen showed an irregular eosinophilic hard tissue mass bearing resemblance to the cross-sectional appearance of the tubular pattern of dentinal tubules [Figure 4],[Figure 5]. There was no evidence of enamel formation.
Unicystic ameloblastomas reported to be composed of hard tissue have belonged to the plexiform intramural proliferation type. , Our case is similar to these reports by Orlowski and Matsumoto. However, unlike earlier reports, there was no evidence of AOT-like areas in our tumour. , Formation of hard tissue in tumours that histologically resemble ameloblastoma or AOT is well-documented in literature. ,,,,,,,, Induction, though a rare occurrence in ameloblastomas, is nevertheless real. 
As early as in 1972, Dunlap and Fritzlen reported the presence of enamel matrix in AOT and they called the tumour an 'adenoameloblastic odontoma'.  Slabbert et al. considered their case to be the first to show evidence of dentinoid induction and named the tumour a 'dentino ameloblastoma'.  Due to the presence of intraepithelial duct-like spaces resembling adenoid spaces, Brannon called their case an 'adenoid ameloblastoma with dentinoid',  a terminology used by the Armed Forces Institute of Pathology and by other authors as well. 
Morphologic recognition of dentin depends on demonstration of dentinal tubules.  In our case, the hard tissue mass resembled a cross section of dentinal tubules, thus, confirming that dentin was the hard tissue in our tumour case. However, examination of the dentinal tubules at a higher magnification did not reveal any odontoblastic process inside. This precluded us from attempting to re-orient the tissue to look for formative cells and eliminated the possibility of de novo induction of the dentin tissue that we encountered. The next possible source of dentin is that it could be a dentin fragment pushed into the jaw in the course of an overambitious root canal treatment.
This fact is substantiated by the correlative past dental treatment history given by the patient. The dentin mass may also be the remnant of an incompletely resorbed deciduous tooth root. Till date, only few reports have described the presence of hard tissue formation in noninductive tumours such as ameloblastomas. The overall biological profiles of such cases can bring out a consensus on whether this group of lesions possesses the potential for laying down tooth matrix and its subsequent designation as a new entity.  Knowledge of conflicting appearances as observed in our case is thus vital to arrive at an accurate assessment of odontogenic tumours with inductive potential.
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