A case of adenomatoid odontogenic tumour (AOT) is presented with a short

review of clinical, radiological and histological features

Czopek, Jacek

Kaczmarzyk, Tomasz

Polish Journal of Pathology

English

Jagiellonian Univeristy Repository

129ADENOMATOID ODONTOGENIC TUMOURJACEK CZOPEK1, TOMASZ KACZMARZYK21Department of Pathomorphology, Jagiellonian University Medical College, Krakow, Poland2Department of Oral Surgery, Jagiellonian University Medical College, Krakow, Poland A case of adenomatoid odontogenic tumour (AOT) is presented with a short review of clinical, radiological and histological features.Key words: adenomatoid odontogenic tumour, AOT. IntroductionAdenomatoid odontogenic tumour (AOT) isa rare, slowly growing, encapsulated, epithelial odon-togenic tumour composed of whorled nodules ofspindle cells, double cell strands and formation ofmicrocystic or duct-like spaces. It has a limitedgrowth potential, and is considered to be a hamar-toma rather than a neoplasm [1, 2].Case reportIn June 2007 an otherwise healthy, 16-year-oldmale was referred by an orthodontist to the Depart-ment of Oral Surgery at the Medical College of theJagiellonian University for extraction of the retainedtooth 43. Two years earlier, he was supplied withorthodontic appliances but no X-ray examinationhad been performed beforehand. Extraoral examination was non-contributory.Intraorally, tooth 43 was not present and teeth 42and 44 were displaced and leaned concurrently.A slight, painless distension of the internal surface ofthe mandibular body in the vicinity of teeth 42, 43and 44 was noted.Orthopantomography revealed a 2 × 3 cm radi-olucency around retained tooth 43 with its apexreaching the inferior border of the mandibular body(Fig. 1). Roots of the neighbouring teeth (particular-ly 42) were displaced concurrently. A tentative diag-nosis of dentigerous cyst was made.Under local anaesthesia, both the retained toothand the cyst follicle were removed. The postoperativeperiod was uneventful.Macroscopically, the pathological specimen con-sisted of a cystic-like follicle (diam. 28 mm) witha tiny tumour in the wall (diam. 7 mm) and thetooth.Microscopically, the tumour was assembled ofspindle-shaped and columnar epithelial cells. Thespindle-shaped cells formed whorled nodules inter-connected by a lattice of thin epithelial strands. Thecolumnar cells lined duct-like spaces with a lumencontaining eosinophilic material. In the stroma, therewere aggregates of eosinophilic hyaline material inbetween the strands of epithelial cells (Figs. 2-4; lensmagnifications: 10×, 20×, 60×, respectively).The diagnosis was: adenomatoid odontogenictumour (No. 1614940).DiscussionThe pathogenesis of AOT is unknown. Thetumour is suspected to develop from residues of thedental lamina and proliferations of odontogenicepithelium adjacent to the reduced enamel epitheli-um of unerupted teeth.The relative frequency AOT varies from 1.7% to7.5% of all odontogenic tumours. Female to maleratio is 1 : 1.9 [1-3].The age range varies between 3 and 82 years [2],but almost 70% of the tumours are diagnosed inpatients in their second decade of life and more than50% in patients between the age of 13 and 19 [3].Few patients are older than 30 years [4].More than 95% of all cases occur within the bone,with a preference ratio of about 2 : 1 for the maxillaover the mandible [1-5]. AOT has a predilection forQUIZCORRECT ANSWER TO THE QUIZ. CHECK YOUR DIAGNOSIS130the canine area; it occurs only rarely in the posteriorregions [1-3].AOT is usually asymptomatic; most of them arediscovered accidentally during a routine radiograph-ic examination. Larger lesions may cause painlessexpansion of the bone. The growth rate of AOT isvery slow and the size of the lesion is between 1.5and 3 cm [1, 2], but there are reports of lesions thatreached a size of 6 to 7 cm [8].A rare peripheral (extraosseous) AOT occurs usuallyin the anterior part of the maxilla and very rarely in themandible [2, 4]. It presents as a pink gingival swelling:the mean age of patients is about 13 years [4]. In imaging studies, AOT usually wraps aroundthe crown or the entire tooth (so-called “follicular”AOT – 70% of all cases), which simulates a dentiger-ous cyst and may be impossible to distinguish froma dentigerous cyst on a radiogram [2-4]. The tumouris well defined and unilocular; in 50-75% of casesalso scattered fine radioopacities may be seen withinthe radiolucent area [2, 4].Rarely the AOT involves the second permanentincisor or the first permanent premolar; involvementof other permanent teeth is rare.An intraosseous AOT unrelated to an uneruptedtooth (“extrafollicular” type) presents as a well-delin-eated radiolucent lesion. It can resemble a residual,a radicular, or a lateral periodontal cyst. It may alsobe located deep in the bone without visible relationto teeth [3]. Sometimes erosion of the alveolar bonecrest, root resorption, perforation of the corticalbone, and invasion of the maxillary sinus is observed[1, 2, 6]. Macroscopically the tumour is well circumscribedand usually encapsulated. Some present as a solidmass. Those situated around the crown of a tooth are(partly) cystic.Histologically AOTs are unrelated to their loca-tion in the jaws; all types show the same pattern. Sol-id lesions consist of a proliferating epithelium sur-rounded by a well-defined fibrous capsule. Variouspatterns are seen in the epithelium. Spindle andpolyhedral cells often form nodules. Several nodulesof various sizes are placed close together with narrowstrands of more orderly arranged epithelial cells inbetween [1, 2].Some epithelial cells form small nests (“rosettes”)often with droplets of an eosinophilic, PAS-positiveJACEK CZOPEK, TOMASZ KACZMARZYKFig. 1.Fig. 2.Fig. 3. Fig. 4.131and diastase resistant, extracellular substance. Cystic(or “duct-like”) spaces of different sizes are seenbetween the nodules but they may not be present inall tumours [1, 2]. The lumen is lined with a layer ofradially arranged columnar or cuboidal, epithelialcells. The cytoplasm is lightly stained, and oval nucleiare polarized away from the lumen. In the lumena thin PAS-positive, diastase-resistant, eosinophilicmaterial is often seen. Some of the cystic structuresmay show invaginations of part of the wall [1, 2].Another distinctive pattern consists of long, nar-row epithelial strands of two layers or a single layerof cubic cells. They form large loops, which are con-nected to each other in a “plexiform” pattern. Thestroma inside the loop is often very loose and some-times missing. This pattern is found in particulartoward the periphery of the lesion. In the stromaa perivascular hyalinization with concentric disposi-tion of hyaline layers in the surrounding connectivetissue and degeneration of the endothelial layer maybe found [2, 6].Calcifications are present in various amounts: theymay be seen in the degenerated epithelium and inthe extracellular, eosinophilic, PAS-positive material[2]. Also an eosinophilic, hyalinized and partly min-eralized, dentinoid-like material and even melaninmay be seen [1, 2, 7].A quite common feature in AOTs is the presenceof minor areas of tumour tissue showing similaritiesto the calcifying epithelial odontogenic tumour.However, it does not change the course of the AOT.The capsule remains intact and recurrence is unlike-ly [2, 8].Mitotic figures may be found occasionally inAOT, but dysplasia has never been described [2].The cystic, follicular variant of AOT has a thickfibrous capsule with a smooth surface. On a section,a large cystic cavity is seen, which is partially filledwith solid tissue showing the same histomorphologyas the solid variant, sometimes with calcifications.Part of the luminal surface of the cystic lesion may becovered with a layer of squamous epithelium similarto dentigerous cysts.Due to rather distinctive microscopic features thediagnosis is usually not difficult. Sometimes AOTmay be mistaken for ameloblastoma, but only theformer is encapsulated and shows duct-like struc-tures within the tumour.If the lesion is small and found in the wall ofa dentigerous cyst, it may be overlooked. The pres-ence of a large amount of calcified material also mayconfuse the pathologist. In common diagnostic prac-tice, immunohistochemistry is not a valuable aid todiagnosis [1, 2, 6]. It may be interesting, however,that only rarely was p53 protein detected in AOTs,in contrast to keratocystic odontogenic tumour,ameloblastoma and clear cell odontogenic carcino-ma, which were reported as positive [2, 9].The treatment of choice is enucleation of thetumour from the bone followed by curettage [1, 2,10]. The risk of recurrence is extremely low; onlyfour cases have been reported [1, 2]. Malignanttransformation has never been described [2].The authors declare no conflict of interest.References1. Philipsen HP, Nikai H. Adenomatoid odontogenic tumour.In: Barnes L, Eveson JW, Reichart P, et al. (eds.). WorldHealth Organization Classification of Tumours. Pathologyand Genetics of Head and Neck Tumours. IARC Press, Lyon2005: 304-305. 2. Praetorius F. Odontogenic tumours. In: Surgical Pathology ofthe Head and Neck. Barnes L (ed.). 3rd ed. Informa Health-care USA Inc., New York 2008; 1201-1338.3. Philipsen HP, Reichart PA. Adenomatoid odontogenictumour: facts and figures. Oral Oncol 1998; 35: 125-131.4. Philipsen HP, Reichart PA, Siar CH, et al. An updated clini-cal and epidemiological profile of the adenomatoid odonto-genic tumour: a collaborative retrospective study. J OralPathol Med 2007; 36: 383-393.5. Swasdison S, Dhanuthai K, Jainkittivong A, et al. Adenoma-toid odontogenic tumors: an analysis of 67 cases in a Thaipopulation. Oral Surg Oral Med Oral Pathol Oral RadiolEndod 2008; 105: 210-215. 6. Leon JE, Mata GM, Fregnani ER, et al. Clinicopathologicaland immunohistochemical study of 39 cases of AdenomatoidOdontogenic Tumour: a multicentric study. Oral Oncol2005; 41: 835-842.7. Aldred MJ, Gray AR. A pigmented adenomatoid odontogenictumor. Oral Surg Oral Med Oral Pathol 1990; 70: 86-89.8. Ledesma-Montes C, Mosqueda Taylor A, Romero de Leon E,et al. Adenomatoid odontogenic tumour with features of cal-cifying epithelial odontogenic tumour. (The so-called com-bined epithelial odontogenic tumour.) Clinicopathologicalreport of 12 cases. Eur J Cancer B Oral Oncol 1993; 29B:221-224.9. Carvalhais J, Aguiar M, Araujo V, et al. p53 and MDM2expression in odontogenic cysts and tumours. Oral Dis 1999;5: 218-222. 10. Zaleska-Szczurek M, Stypułkowska J, Stachura J, KaperaP. Adenomatoid odontogenic tumor – a rare odontogenicneoplasm of the jaws in own clinical material. Poradnik Stom-atologiczny 2004; 8: 34-40.ADENOMATOID ODONTOGENIC TUMOURTHE AUTHORS OF CORRECT DIAGNOSIS ARE:Maciej Znaniecki MD, Janusz Korczak Memorial Provincial Specialistic Hospital in Słupsk, Departament of Pathomorphology, ul. Hubalczyków 1, 76-200 SłupskJacek Kowalski MD, Saint Adalbert Memorial Specialistic Hospital, Department of Pathomorphology,Al. Jana Pawła II 50, 80-046 GdańskElżbieta Trojnar, Provincial Hospital No2 in Rzeszów, Department of Pathomorphology, ul. Lwowska 60, 35-301 Rzeszów

Adenomatoid odontogenic tumour

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Adenomatoid odontogenic tumour

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