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Atypical ameloblastoma – an enigma in diagnosis review of literature and report of a case


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Atypical ameloblastoma – an enigma in diagnosis review of literature and report of a case

  1. 1. J Clin Exp Dent. 2011;3(1):e60-5. Atypical ameloblastoma.Journal section: Oral Medicine and Pathology doi:10.4317/jced.3.e60Publication Types: Case Report Atypical ameloblastoma – an enigma in diagnosis: review of literature and report of a caseThomas George 1, Kundendu A. Bishen 21 MDS, Visiting senior lecturer, Department of oral pathology, oral medicine & periodontology, Faculty of dentistry, University ofMalaya.2 MDS, Lecturer, Oral and Maxillofacial Pathology, Mahatma Ghandhi Dental College and hospital, Jaipur.Correspondence:Department of Oral Pathology,Mahatma Ghandhi Dental College and hospital,RIICO, Institutional area, Sitapura,Jaipur, Rajasthan, India - 302022E-mail add: kundendu@hotmail.comReceived: 25/06/2010Accepted: 06/08/2010 George T, Bishen KA. Atypical ameloblastoma – an enigma in diagnosis: review of literature and report of a case. J Clin Exp Dent. 2011;3(1):e60-5. Article Number: 50344 © Medicina Oral S. L. C.I.F. B 96689336 - eISSN: 1989-5488 eMail: Abstract Ameloblastoma, a benign neoplasm of jaw bones is the most common of all odontogenic tumors. Its pathology is generally well understood and is easy to diagnose. This article presents a rare case of an ameloblastoma with atypical features depicting an example of the diagnostic difficulty posed by some ameloblastomas and briefly re- views the classification and literature of odontogenic malignancies. This case is unusual in the fact that although the clinical presentation was suggestive of a malignancy, the histological features were not sufficient to warrant the lesion as malignant. Albeit, the features of epithelial dedifferentiation were evident at post operative histopatholo- gical evaluation but no proof was available to authenticate frank metastasis or carcinoma. The case was diagnosed as an atypical ameloblastoma and frequent follow up was recommended. This article discusses about ameloblastic carcinoma, other odontogenic malignancies and emphasizes the need for standardization and quantification of the fundamental concepts of odontogenic malignancies for more reliable and early diagnosis for better treatment and prognosis. Key words: Atypical ameloblastoma, proliferative ameloblastoma, ameloblastic carcinoma. e60
  2. 2. J Clin Exp Dent. 2011;3(1):e60-5. Atypical ameloblastoma.Introduction pable and tender. Radiographic examination of the man-Of all the odontogenic tumors, the pathology of ame- dible revealed a multilocular destructive lesion in 37, 38loblastoma – being the most common is generally well region involving the body and ramus of mandible and 36understood. However the concept of odontogenic ma- showed root resorption. The chest radiographs did notlignancies has been a subject of considerable discussion demonstrate pulmonary lesions and hematological andand controversy for many years. The term ameloblastic biochemical investigations were unremarkable. Ultra-carcinoma is used to designate a lesion with histological sound revealed a fatty liver.evidence of malignancy in primary tumor, regardless of Based on the above findings, a diagnosis of ameloblas-whether it has metastasized (1). The malignant epithelial toma was made and patient underwent a hemimandibu-proliferation may initially be present with a resemblance lectomy procedure and submandibular glands were alsoto an ameloblastoma (de novo ameloblastic carcinoma) removed. The excised tissue was sent for further histo-or sometimes an ameloblastoma may show features of pathological evaluation. Postoperative recovery wasepithelial dedifferentiation overtime (ameloblastic car- uneventful and patient was advised a follow up exami-cinoma ex-ameloblastoma) (2). If the anaplastic fea- nation after 3 months.tures are not sufficient to justify an ameloblastoma as The excisional tissue grossly showed a large swellingmalignant, it can be called as atypical ameloblastoma extending from 36 to the angle of mandible. The buccal(3). Ameloblastic carcinoma is a rare odontogenic ma- side showed a large cystic cavity where as the linguallignancy that challenges the diagnostic acumen of the aspect showed a solid proliferation of the tumor masspathologists as the understanding of the identifying his- showing necrotic area in centre. The occlusal aspecttological features of the tumor is some what vague and showed 33, 34, 35, 36 and an ulcerated area posterior tonot standardized/quantified. We herein report a rare case 36 (unhealed extraction socket) (Fig. 1).of ameloblastoma which had an aggressive behaviorand histologically had areas of cytological atypia whichwarrant a more aggressive surgical approach and followup. The purpose of this article is to emphasize the needfor standardization and quantification of the fundamen-tal concepts of odontogenic malignancies for more relia-ble and early diagnosis because this has a direct bearingon the treatment plan and prognosis.Case ReportA 58 years old male patient reported to the out patientdepartment of Manipal college of dental sciences, Man-galore in February 2007 with the chief complaint of anon tender swelling of 2 years duration on the left side ofhis face. The swelling had started as a small peanut sizebulge and had gradually increased to the present size. Fig. 1. Gross appearances of the specimen from occlusal viewThe patient gave no history of fever, malaise, associated showing expansion of the buccal and lingual cortical plates withpain or parasthesia or dysphagia. The past medical his- unhealed socket in relation to 37tory revealed that an incisional biopsy had been perfor- Microscopically, the tissue sections from the buccal as-med previously which was suggestive of ameloblastoma. pect showed a characteristic lining suggestive of a uni-Family history was non contributory and social history cystic ameloblastoma consisting of a basal layer of talldisclosed a chronic alcoholic with a habit of chewing columnar ameloblast like cells exhibiting reversal of po-tobacco with betel quid for past 20 years. larity. The superficial layers consist of several rows ofClinically, patient had a medium built and was poorly stellate reticulum like cells. Focal areas of lining epithe-nourished, conscious and cooperative. On local exami- lium showed flattened basal cells. Proliferations of thenation, a diffuse swelling of size 2×3 cm was present lining epithelium into the lumen as well as underlyingextraorally on the left side of face corresponding to the connective tissue were also observed. The mural as wellangle of mandible. The swelling was non tender, firm in as the luminal proliferations showed plexiform amelo-consistency and had a smooth texture. Intraoral exami- blastoma with areas of microcyst formation arising as anation revealed an unhealed extraction socket in relation result of stromal degeneration. The stromal blood vesselsto 37 and expansion of buccal and lingual cortical plates. showed degenerative changes appearing only as ghostlyThere was no dysphagia, pain or paresthesia. outlines surrounding few inflammatory cells.The teeth present in the area showed no mobility or The sections from the unhealed socket area revealed ul-loosening. Left submandibular lymph nodes were pal- cerated parakeratinised stratified squamous epithelium e61
  3. 3. J Clin Exp Dent. 2011;3(1):e60-5. Atypical ameloblastoma.with epithelial proliferation noted at the margin of ulcer.Deeper in the connective tissue the epithelial prolifera-tion from the margin of ulcer merged with the plexiformameloblastoma.The sections taken from the lingual aspect revealed afollicular ameloblastoma showing numerous small andlarge sized ameloblastomatous follicules with a centralcore of stellate reticulum like cells and areas of cysticdegeneration. Sheets of odontogenic epithelial cells wi-thin the connective tissue demonstrated extensive ce-llular pleomorphism with cells varying from ovoid tospindle in shape (Fig. 2). Occasional mitosis (typicaland atypical) was evident within the sheets of odontoge-nic epithelium along with other features like increasednuclear cytoplasmic ratio, prominent nucleoli (Fig. 2). Fig. 3. Areas of degeneration,hemorrhage and necrosis However, the epithelial dedifferentiation as seen in the present case, is not enough to warrant the ameloblasto- ma as malignant. Such tumors can be called as atypical ameloblastoma (3). Ameloblastic carcinoma is a malignant odontogenic tu- mor, the diagnosis of which is as enigmatic, as was its position in the classification of odontogenic malignan- cies. The term Ameloblastic carcinoma was acknowled- ged by the World Health Organization (WHO) (2) as late as in 2002. The classification of odontogenic malignan- cies and the concept of malignancy in ameloblastoma is a controversial topic which has been discussed for long. Various classifications have been developed to categori- ze ameloblastic carcinomas (2-5). The WHO published its classification for malignant neoplasms and other tumors related to the odontogenicFig. 2. Dysplastic cells exhibiting occasional atypical mitoses with apparatus in 1972 and recognized the following subty-cellular pleomorphism pes: Odontogenic carcinomaIn addition, dominant areas on lingual aspect showed A. Malignant ameloblastomasheets of squamoid cells exhibiting dyskeratosis with B. Primary intraosseous carcinoma (PIOC)interspersed areas of extensive hemorrhage, degene- C. Other carcinoma arising from odontogenic epithe-ration and necrosis (Fig. 3). Few multinucleated giant lium including those arising from odontogenic cystcells were also evident. The submandibular nodes were In this initial attempt to classify odontogenic carcinomas,completely free of tumor. Based on the above findings a the WHO failed to specifically delineate ameloblasticdiagnosis of atypical ameloblastoma was given. carcinomas. This WHO classification system recognized and distinguished PIOC from malignant ameloblastomaDiscussion but it did not consider the possibility that a squamousThe typical ameloblastoma is a histologically benign tu- cell carcinoma could arise in a pre-existing ameloblas-mor but it has considerable tendency to recur and even toma and had no sub-division under which such entitiescause death by invasion of vital structures. Although it could be locally invasive, it rarely shows metastatic dissemi- Initially, the term ameloblastic carcinoma was introdu-nation. In a malignant ameloblastoma both the primary ced to describe ameloblastomas in which there had beenas well as the metastatic deposits has the typical histo- histological malignant transformation in associationlogical features of ameloblastoma. On the other hand, with less differentiated evidence of metastatic growths.histological evidences of malignancy in the primary or Such tumors showed features of ameloblastoma inter-recurrent tumor, regardless of whether it has metasta- mingled with those of carcinoma.sized, characterize it as an ameloblastic carcinoma (1). Elzay (4) in 1982 suggested that the WHO classification e62
  4. 4. J Clin Exp Dent. 2011;3(1):e60-5. Atypical modified to permit the separation and recognition of Elzay (4). And they proposed that for giving a correctclosely related entities. So he classified all intraosseous diagnosis, the taxonomic problem can be avoided by as-carcinoma under the heading of PIOC and then those tu- suming that ameloblastic carcinomas can arise not onlymors were subclassified and subtyped according to his- de novo or from a well differentiated ameloblastoma buttological evidence of origin. The proposed classification also from other sources of odontogenic epithelium eg.was as follows: odontogenic cyst. Thus, the main difference betweenPrimary Intraosseous Carcinoma Elzay’s (4), and Slootweg and Müller’s (5) schemes re-Type 1 – Arising ex odontogenic cyst lates to the minor point of histogenesis.Type 2 – Arising ex ameloblastoma In 1992, a modified WHO classification system for the a) Well differentiated - Malignant ameloblastoma odontogenic carcinomas was published (7), including b) Poorly differentiated - Ameloblastic carcinoma the following categories:Type 3 – Arising de novo Odontogenic carcinoma a) Non-keratinizing A. Malignant ameloblastoma b) Keratinizing B. Primary intraosseous carcinomaAccordingly, the PIOC type II recognized the potential (de novo, ex ameloblastoma, ex odontogenic cyst)for malignification of ameloblastoma with varing degree C. Malignant variants of other odontogenic epithe-of differentiation. Hence II A was reserved for tumors lial tumorswhich histologically demonstrated proper ameloblasto- D. Malignant changes in odontogenic cystma in the jaw and in any metastatic lesion. In essence, Inspite of all the proposals made, it failed to recognizesuch tumors would be well differentiated where as the ameloblastic carcinoma as a separate entity. Since thetype II B sub classification was reserved for less diffe- WHO classification did not recognize the existence ofrentiated tumors having histological features of amelo- ameloblastic carcinoma, all such lesions had to be clas-blastoma and squamous cell carcinoma concomitantaly. sified either as PIOC or as malignant ameloblastoma.Two years later, in 1984, Slootweg and Müller (5) pu- Because of this overlapping of terminologies, the po-blished a paper reviewing 42 cases of malignant ame- tential of the histological diagnosis to distinguish theloblastoma (according to WHO) and adding 2 more to biologic behavior, prognosis and treatment plan of thethe list. They pointed out that some cases of PIOC may ameloblastic carcinoma and closely related tumors washave areas that are morphologically similar to malignant hindered. This taxonomic problem continued for a de-ameloblastoma. Thus there is a possibility that a PIOC cade and finally ended in 2002 when ameloblastic carci-would have been classified as a malignant ameloblasto- noma was recognized by the WHO in its revised versionma if metastasis had occurred or as a PIOC if metastasis by Philipsen and Reichart (2).had not occurred. They also pointed out that matters had The categories identified in the WHO’s revised versionbeen further complicated because of no distinction bet- 2002 (2) were:ween malignant ameloblastoma and ameloblastic carci- Odontogenic carcinomanoma. They said that the WHO classification of odon- A. Metastasizing ameloblastomatogenic carcinoma should be revised in some aspects. B. Ameloblastic carcinomaThey advocated the modification proposed by Elzay (4) * Primary (=de novo)and proposed a slight modification taking in account the * Carcinoma ex ameloblastoma (=dedifferen-various possible origins of PIOC. So the classification tiated)they proposed was: * PeripheralPrimary Intraosseous Carcinoma C. Primary intraosseous carcinomaType 1 – Primary intraosseous carcinoma ex odontoge- * Solidnic cyst * CystogenicType 2 – Primary intraosseous carcinoma arising ex D. Ghost cell odontogenic carcinomaameloblastoma E. Clear cell odontogenic carcinoma a) Malignant ameloblastoma Thus, the term “ameloblastic carcinoma” was used by b) Ameloblastic carcinoma, arising de novo, ex ame- Shafer, Elzay(4), Slootweg and Müller’s (5), primarilyloblastoma or odontogenic cyst to convey the presence of cytologic features of malig-Type 3 – Primary intraosseous carcinoma arising de nancy in an ameloblastoma came into being and got re-novo cognized. a) Non-keratinizing Ameloblastic carcinoma is considered to be a rare odon- b) Keratinizing togenic malignancy. Akrish et al. (6) analyzed all theSo, they accepted that malignant ameloblastoma and published cases in English language literature betweenameloblastic carcinoma be included under the encom- the years 1984 and 2004 to find only 37 cases reportedpassing term “PIOC ex ameloblastoma” as proposed by in addition to the case presented in the paper (making a e63
  5. 5. J Clin Exp Dent. 2011;3(1):e60-5. Atypical of 38 cases). It might be that, because of the pro- to distinguish between ameloblastoma, atypical amelo-longed controversy around ameloblastic carcinoma it blastoma and ameloblastic carcinoma are not standar-was either wrongly categorized or less reported. Unfor- dized/ quantified. Many important questions/conceptstunately, as a consequence of this, the understanding of remain unanswered e.g. Is the diagnosis of atypicalthe identifying clinical and histological features of the ameloblastoma of any relevance for treatment options?tumor is still some what vague and not standardized/ What features are necessary to differentiate between the-quantified. se closely related lesions? Which histologic feature isAlthough Corio et al. (1) had reported the mean age of a sine qua non for diagnosing a particular odontogenicoccurrence to be 30.1 years with no gender predilec- malignancy? If two lesions have an overlapping featurestion, recently Akrish et al. (6) reported the mean age of e.g. Presence of mitotic figures or a high proliferative in-occurrence to be 52 years and the male to female ratio dex, how many mitoses per high power field or what per-being 1.5 to 1. The posterior mandible was the most fa- cent of cells showing high index should distinguish twovored site in both the reports. Radiographically the tu- closely related lesions? We hereby strongly propose thatmor resembles ameloblastoma and mostly appears as a the fundamental concepts of odontogenic malignanciesmultilocular radiolucency. Clinically the patients mostly should be standardized and quantified for more reliablecomplain of expansion, a hard mass, rapid growth, fa- and early diagnosis because this has a direct bearing oncial asymmetry, a nonhealing extraction site, an ulcer, the treatment plan and prognosis.a fistula or perforation of the cortex. These clinical fea- To conclude, the present case is an example of the diag-tures though suggestive of a malignancy, are again not nostic difficulty posed by some ameloblastomas. Thispathognomonic. In the present case also the patient had case is unusual in the fact that although the age, rapiditymost of these features. of growth and clinical presentation were suggestive of aHistologically ameloblastic carcinoma demonstrates malignancy, the histological features were not sufficientmore cytologic atypia and mitotic activity than ame- to warrant the lesion as malignant. Albeit, the features ofloblastoma. It includes the features of epithelial dedi- epithelial dedifferentiation were evident at post operativefferentiation. There is lack of evidence of reverse po- histopathological evaluation but no proof was availablelarization, sheets of disordered mitotically active small to authenticate frank metastasis or carcinoma. Hence inbasaloid cells with dark nuclei; larger squamoid or po- the light of current concepts the tumor was categorizedlygonal cells with vesicular nuclei; or elongated spin- as an ameloblastoma with atypical features and frequentdled epithelial cells (6). The histological diagnosis is not follow up was easy one and a pathologist must rule out a lexicon ofdifferential diagnosis which includes the typical amelo-blastoma, metastatic carcinoma to the jaw, intra bony ex-tension of a surface mucosal carcinoma, central salivarygland tumor, PIOC, acanthomatous ameloblastoma, ke-ratoameloblastoma, squamous odontogenic tumor, andcalcifying epithelial odontogenic tumor. In the presentcase also all these differential diagnoses were ruled outas elaborated by Coiro et al. (1)Until 2004, the terms aggressive or proliferative ame-loblastoma, ameloblastic carcinoma and atypicalameloblastoma were used synonymously by some in-vestigators (7). In 2004 Slater (3) suggested that ame-loblastomas which exhibit basilar hyperplasia and an in-creased mitotic index should be designated as “atypicalameloblastomas” or “proliferative ameloblastomas” be-cause these findings are probably insufficient to permita diagnosis of ameloblastic carcinoma in the absence ofnuclear pleomorphism, perineural invasion or other his-tologic evidence of malignancies (3). The picture is fur-ther complicated by the fact that although the presenceof abundant mitotic figures is one of the most importantdiagnostic criteria, the prognostic significance of this isnot known (8).The enigma about the diagnosis of ameloblastic carcino-ma is further aggravated because the diagnostic criteria e64
  6. 6. J Clin Exp Dent. 2011;3(1):e60-5. Atypical ameloblastoma.References1. Corio RL, Goldblatt LI, Edwards PA, Hartman KS. AmeloblasticCarcinoma: A clinicopathologic study and assessment of eight cases.Oral Surg Oral Med Oral Pathol. 1987;64:570-6.2. Philipsen HP, Reichart PA. Revision of the 1992-edition of the WHOhistological typing of odontogenic tumours. A suggestion. J Oral Pa-thol Med. 2002;31:253-8.3. Slater LJ. Odontogenic malignancies. Oral Maxillofac Surg ClinNorth Am. 2004; 16:409-24.4. Elzay RP. Primary intraosseous carcinoma of the jaws. Review andupdate of odontogenic carcinomas. Oral Surg Oral Med Oral Pathol1982; 54:299-303.5. Slootweg PJ, Müller H. Malignant ameloblastoma or ameloblasticcarcinoma. Oral Surg Oral Med Oral Pathol. 1984;57:168-76.6. Akrish S, Buchner A, Shoshani Y, Vered M, Dayan D. Ameloblasticcarcinoma: report of a new case, literature review, and comparison toameloblastoma. J Oral Maxillofac Surg. 2007;65:777-83.7. Ameerally P, McGurk M, Shaheen O. Atypical ameloblastoma: re-port of 3 cases and a review of the literature. Br J Oral MaxillofacSurg. 1996;34:235-9.8. Gardner DG.Some current concepts on the pathology of ame-loblastomas. Oral Surg Oral Med Oral Pathol Oral Radiol Endod.1996;82:660-9. e65