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Acta Odontológica Latinoamericana

versión On-line ISSN 1852-4834

Acta odontol. latinoam. vol.22 no.2 Buenos Aires set. 2009

 

ARTÍCULOS ORIGINALES

Radiographic interpretation of unilocular radiolucent mandibular lesions

 

Ricardo Raitz1, Luciana Correa2, Marlene Fenyo-Pereira1

1 Oral Radiology Division, School of Dentistry, University of São Paulo.
2 General Pathology Division, School of Dentistry, University of São Paulo.

CORRESPONDENCE Dr. Ricardo Raitz Rua Heitor Penteado, 1832, 101/A Sao Paulo, Brazil. Phone: (55 11) 3673 5270 / Fax: (55 11) 3673-5270 E-mail: ricardoraitz@ig.com.br


ABSTRACT

The main goal of this study was to identify the main distinctive radiographic characteristics of different unilocular radiolucent mandibular lesions based on the criteria used by different groups of specialists during the process of radiograph interpretation to arrive at a correct diagnosis. A total of 24 panoramic radiographs were selected exhibiting the following lesions: ameloblastoma, keratocystic odontogenic tumor, dentigerous cyst and simple bone cyst. Six cases of each pathology were analyzed by 3 specialists from 4 related areas (pathologists, stomatologists, radiologists and oral surgeons). A number of important distinctive features and confounding characteristics that are liable to misinterpretation were pointed out by the specialists during the analysis. The method of generalized estimating equations (GEE) was used to estimate the probability of correct diagnosis according to the specialization of the examiner and the type of lesion and no significant relation was found (p>0.05 for all variables). The overall percentage of correct diagnosis among the specialists was around 56%, which shows that these lesions are of difficult radiographic diagnosis. Although the specialty of the examiners did not influence the results, i.e., the 4 different kinds of specialists showed the same diagnostic capacity, the criteria used for interpreting the same lesions were often different among the specialists. The compilation of these criteria enabled the identification and selection of some useful distinctive radiographic characteristics to formulate diagnostic hypothesis of unilocular radiolucent lesions. The radiographic diagnosis of the unilocular radilucent mandibular lesions is particularly difficult and the histopathological examination is essential to make the definitive diagnosis.

Key words: Odontogenic cysts; Odontogenic tumours; Radiography; Panoramic.

RESUMO

Interpretação radiográfica de lesões radiolúcidas uniloculares mandibulares

O objetivo deste estudo foi identificar as principais caracteristicas radiograficas para a diferenciacao de lesoes radiolucidas uniloculares mandibulares, por meio dos criterios utilizados por diferentes grupos de especialistas durante o processo de interpretacao radiografica para a obtencao dos diagnosticos corretos das lesoes. Vinte e quatro radiografias panoramicas foram selecionadas exibindo as seguintes lesoes: ameloblastoma, tumor odontogenico queratocistico, cisto dentigero e cisto osseo simples. Seis casos de cada entidade patologica foram analisados por 3 especialistas de 4 areas diretamente relacionadas a diagnostico (patologistas, estomatologistas, radiologistas e cirurgioes buco-maxilo-faciais). Inumeras caracteristicas importantes tanto para a correta distincao quanto para a ocorrencia de confusao entre as lesoes, foram levantadas pelos especialistas durante a analise. O metodo de equacoes de estimacao generalizada (EEG) foi utilizado para estimar a probabilidade do acerto do diagnostico segundo a especialidade do examinador e o tipo de lesao, nao sendo encontrada relacao significativa (p>0.05 para todas as variaveis). A porcentagem geral de diagnostico correto entre os especialistas ficou em torno de 56%, o que mostra que estas lesoes sao de dificil diagnostico radiografico. Embora a especialidade dos examinadores nao tenha influenciado os resultados, isto e, os 4 tipos de especialistas mostraram a mesma capacidade diagnostica, os criterios utilizados para a interpretacao das mesmas lesoes foram frequentemente diferentes entre os especialistas. A compilacao desses criterios possibilitou a identificacao e selecao de algumas caracteristicas radiograficas distintivas uteis na formulacao de hipoteses diagnosticas de lesoes radiolucidas uniloculares. O diagnostico radiografico das lesoes radiolucidas uniloculares mandibulares e particularmente dificil e a analise histopatologica e essencial para a obtencao do diagnostico definitivo.

Palavras chave: Cistos odontogenicos; Tumores odontogenicos; Radiografia panoramica.


 

INTRODUCTION

The lesions that can present a unilocular and welldefined radiolucent image with a well corticated border, which may or not include an unerupted tooth, have been studied using various imaging techniques: magnetic resonance imaging1, scintigraphy2, ultrasonography3, computed tomography4, digital radiography5 and conventional radiography6-8. Ameloblastoma, keratocystic odontogenic tumor, dentigerous cyst and simple bone cyst are examples of such lesions and although they are treated differently, they are extremely similar in terms of clinical and radiographic characteristics. This makes the radiographic differentiation of these lesions a difficult task. Although the image analysis itself does not lead to the final diagnosis, a careful consideration of the location of the lesion, its borders and radiographic aspect, as well as the effects of the lesion on adjacent structures, enables a better interpretation and understanding. The presence and extension of cortical erosion, root resorption or divergence can also aid dentists in establishing a diagnosis9. Thus, it is of great importance to establish reliable criteria and identify tenuous differences between these lesions, allowing higher rates of correct diagnosis. However, different specialists employ their own experience and knowledge.
The main goal of this study was to identify the main distinctive and confounding (liable to misinterpretation) radiographic characteristics of different unilocular radiolucent mandibular lesions based on the criteria used by different groups of specialists during the process of radiograph interpretation to arrive at a correct diagnosis.

MATERIALS AND METHODS

Twenty-four panoramic radiographs were selected and distributed into 4 groups of 6 radiographs each, according to the following pathologic processes: ameloblastoma, keratocystic odontogenic tumor, dentigerous cyst, simple bone cyst. All panoramic radiographs used in this study were considered technically diagnostic by 3 radiologists, who were not included in the group of examiners. The unilocular feature was also confirmed by them and/or by computed tomography. All histopathological reports were revised by an oral pathologist, confirming the actual diagnosis corresponding to each radiograph. Image assessment was performed by 12 specialists with over 5 years’ experience. These specialists were professors in the following areas: 3 pathologists (P), 3 stomatologists (S), 3 radiologists (R), and 3 oral surgeons (Su). The radiographs were randomly presented to these examiners, who did not know how many cases of each lesion were included in the study. The examiners were told to establish the most probable diagnosis based on the analysis of each radiograph using their own diagnostic methods and radiographic experience, and to list the three most important criteria used to establish their diagnosis. No clinical information was given to the examiners. All the criteria used by the examiners to correctly identify a lesion were tabulated. Using generalized estimating equations (GEE)10, the probability of correct diagnosis was calculated, taking into account the specialization of the examiner and the type of lesion. All assessments took place in the same room and were carried out using the same x-ray illuminator and light intensity. The examiner performed all analyses on the same day. This protocol was independently reviewed and approved by the institutional ethical review board of the University.

RESULTS

The results showed that the overall percentage of correct diagnosis among the specialists was around 56%, and only slight variations were observed for each specialization: radiologists, 54.17%; pathologists, 55.56%; oral surgeons, 54.17%; and stomatologists, 61.11%. Table 1 shows the discrepancy among the percentages of correct diagnosis performed by the specialists in the different cases of the same lesion.

Table 1: Percentage of correct diagnoses per case.

Evaluation of the diagnoses made by the specialists (Table 2) showed that ameloblastoma was the most frequent diagnosis (35.66% of the times). The least frequent was simple bone cyst (17.83% of the times). Using the method of GEE10, it was observed that no variable (specialization or type of lesion) was significantly related to the probability of correct diagnosis. Also, no specific criterion used was related to the specialties (p > 0.05 for all variables) (Table 3). Table 4 shows the compilation of the most relevant and cited differences among the 4 lesions identified by the examiners.

Table 2: Number (absolute and relative frequency) of selected diagnoses.

Table 3: Probability of correct diagnoses.

Table 4: Compilation of 8 distinctive radiographic characteristics, given by different specialists.

DISCUSSION

Diagnosis of unilocular radiolucent lesions of the mandible is particularly difficult due to the great radiographic similarity among the 4 pathologies studied. The radiographic diagnosis of these lesions by the specialists was accurate in around 56% of the 24 cases analyzed. Ameloblastoma was the most frequent diagnosis (35.66% of the times) and simple bone cyst was the least frequent diagnosis (17.83% of the times). It is interesting to observe such a discrepancy, since the same number of cases was used for all lesions (6 cases of each). Among all the lesions studied, ameloblastoma was the one with the most distinctive characteristics and severe clinical consequences, and is the pathology that requires the most radical treatment. By and large, it is the lesion that concerns dentists the most, which may explain the results obtained. In addition, cases of ameloblastoma are thoroughly studied in schools of Dentistry and Hospitals, whereas simple bone cyst cases are not; this is a lesser-discussed lesion, particularly because it is rare and does not bring serious consequences to the patient11,12. Diagnostic exploratory surgery suffices to confirm a case of simple bone cyst. This is probably why it was the least mentioned diagnosis among the specialists. Using GEE10, the probability of correct diagnosis was modeled according to the following variables: specialization of the examiner and type of lesion (Table 3). We can conclude that the probability of correct diagnosis is not related to the factors assessed. The analysis of the diagnostic criteria selected by each of the 12 specialists revealed their profound knowledge, which stems from their individual experience. Upon analysis of each case studied, we observed that, many times, the different specialists used different criteria to diagnose the same case. If one examiner had considered some of the criteria used by the other examiners (Table 4), certainly his/her percentage of correct diagnosis would have been higher (unpublished data).
Some conclusions could be drawn from the analysis of the percentage of correct diagnosis and the criteria used in some specific cases (Table 1). Regarding the high percentage of correct diagnosis in cases 7, 18 and 20 (ameloblastoma), these cases were probably correctly diagnosed as ameloblastoma because they presented extremely aggressive lesions with great tissue destruction. However, albeit erroneous, an often-used criterion was the multilocular aspect of the lesion. Indeed, ameloblastoma is usually reported as a multilocular lesion, although our sample comprised unilocular cases only, confirmed by the previous analyses of 3 radiologists and/or by computed tomography. According to Mc Ivor (1972)13, the lesions generally appear to be multilocular in panoramic radiographs, causing misinterpretation, especially when they present a corticated and festooned border. Using occlusal radiographs, we can observe that this appearance is probably due to perforation or depression of either the buccal or lingual cortical plates. A unilocular lesion partially divided by a septum can also produce a similar image. A serious problem in the diagnosis of ameloblastoma is its similarity to dentigerous cysts (Fig. 1), caused by the relation between the tooth and the lesion. In the case shown in figure 1, the lesion caused distal displacement of the molar, but the border of the lesion did not seem to touch the tooth. This means that the lesion was not caused by the tooth, the sine qua non of dentigerous cysts11. Another fundamental factor, not easily assessed by most of the examiners, is the growth pattern of the lesions. According to the successful examiners, a vertical growth pattern is more frequent in cases of ameloblastoma, sometimes causing convexity at the inferior border of the mandible. The buccolingual growth pattern is more frequent in cases of dentigerous cyst.


Fig. 1
: Ameloblastoma: this lesion caused distal displacement
of the molar and bulging of the mandibular base. Note that the distal border of the lesion seems to be beyond the tooth.

Some cases had a lower percentage of correct diagnosis among the specialists, such as case 13 (ameloblastoma) (Fig. 2). This case presented a small, non-destructive lesion with no tooth resorption, and was usually mistaken for keratocystic odontogenic tumor. In case 13, even though the lesion had a distinct border, only a tenuous halo could be observed and the tooth seemed to be “floating” within the lesion, which should lead to the diagnosis of ameloblastoma8. Only 16% of the examiners made this interpretation. With regard to keratocystic odontogenic tumor, a high rate of correct diagnosis was not observed in any case (Table 1). This means that keratocystic odontogenic tumor is the lesion with the fewest specific characteristics for the examiners, because even in cases where there was clear anteroposterior growth, lobular or festooned borders and a radiopaque halo, well-defined diagnostic characteristics that have been well established in the literature14, some of the examiners failed to make a correct diagnosis. In our sample, two cases with these characteristics (Fig. 3) had a percentage of correct diagnosis of 66%.


Fig. 2
: Ameloblastoma: this small and round shaped lesion was usually mistaken for Keratocystic odontogenic tumor. The intense radiopaque halo is not present and the tooth seems to be “floating” within the lesion.


Fig. 3
: Keratocystic odontogenic tumor: this lesion clearly shows
an anteroposterior growth, lobular or festooned borders and intense radiopaque halo, which is strongly suggestive for its diagnosis.

Aggressive lesions are generally related to ameloblastoma and not to dentigerous cyst. Figure 4 shows an unusual case of dentigerous cyst (case 6) that had a percentage of correct diagnosis of only 8%, since it is a large lesion and caused the resorption of the first and second molars. All the criteria used by the specialists are essential for diagnosis. Some criteria, however, require more specific examination because of their great importance when diagnosing a lesion and because slight variations may be present in each type of lesion. This is the case of root resorption, a criterion that requires careful examination, according to the examiners. In 1976, Struthers and Shear15 observed variations in the degree of root resorption caused by unilocular radiolucent lesions. They concluded that ameloblastoma causes a higher degree of generalized resorption than that observed in other lesions. However, dentigerous cysts can also cause major root resorption, leading to the complete resorption of the distal root of the adjacent tooth, especially late in the course of the disease. The fact that dentigerous cysts originate in the tooth follicle may explain their root-resorption capacity, and their capacity to cause resorption of the predecessor tooth mimics a physiological process. There is, in general, no root resorption in cases of keratocystic odontogenic tumor. This is probably because this lesion grows within the medullary cavity, causing no resorption of the alveolar border, lingual cortical plate or buccal cortical plate15, associated to the imbalance of the expression of some molecules16.


Fig. 4
: Dentigerous cyst: this large and old lesion caused the resorption of the first and second molars. These characteristics often resemble those of Ameloblastoma.

The cases in which dentigerous cysts were small and centrally related to the tooth, vastly discussed in the related literature8,9,11, had a higher percentage of correct diagnosis. For the examiners who correctly diagnosed most of the dentigerous cysts cases, they are more commonly found in the region of the third molar and rarely reach the dimensions of ameloblastoma, even in cases of unilocular ameloblastoma. Since simple bone cyst does not grow with pressure, it does not cause tooth displacement, which gives the lesion its scalloped appearance17. In addition to this characteristic, the case shown in Figure 5 reveals the young age of the patient and the anterior location of the lesion, which presents lack of radiolucent homogeneity, the most important criteria used to correctly identify these cases. Some lesions (cases 5 and 19) appeared to have different degrees of radiolucency, revealing a certain internal fogging, a fact that has already been described in the related literature17 (Fig. 5). Some cases were incorrectly diagnosed (25-33% of correct diagnosis) by the specialists more often because they were, for the most part, mistaken for ameloblastoma (Fig. 6). However, the absence of precise delimitation and the partial presence of trabecular bone17 should lead to the diagnosis of simple bone cyst, according to a few examiners.


Fig. 5
: Simple bone cyst: this young patient presented an anterior lesion with different degrees of radiolucency, revealing a certain internal fogging.


Fig. 6
: Simple bone cyst: this case shows the absence of precise delimitation and the partial presence of trabecular bone.

Another important factor to be considered when diagnosing simple bone cyst is the presence of double radiopaque lines7. This image results from the expansion of the lesion to both buccal and lingual plates without total alveolar resorption. If we collect and study data regarding observation and if we identify what determines the scope and accuracy of observation, it is likely that we will be able to substantially improve the teaching of observation parameters and the role of interpretation in medical education and medical practice, and perhaps even in oral and maxillofacial radiology. Although the probability of making a correct diagnosis is not related to any specialty, different criteria for interpreting the same lesions could be observed. Table 4 shows the compilation of the most important distinctive radiographic characteristics, given by different specialists when analyzing unilocular radiolucent mandibular lesions. The radiographic diagnosis of the unilocular radilucent mandibular lesions is particularly difficult and the histopathological examination is essential to make the definitive diagnosis.

ACKNOWLEDGEMENTS

Thanks to Professor Lilian Nati (PhD in Statistics) for the statistical work and to AC Camargo Hospital for the radiographs.

REFERENCES

1. Minami M, Kaneda T, Ozawa K et al. Cystic lesions of the maxillomandibular region: MR imaging distinction of odontogenic keratocysts and ameloblastomas from other cysts. Am J Roentgenol 1996;166:943-949.         [ Links ]

2. Hofer B, Hardt N, Voegeli E, Kinser J. A diagnostic approach to lytic lesions of the mandible. Skeletal Radiol 1985; 14:164-172.         [ Links ]

3. Lauria L, Curi MM, Chammas MC, Pinto DS, Torloni H. Ultrasonography evaluation of bone lesions of the jaw. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1996;82:351-357.         [ Links ]

4. Nortje CJ, van Rensburg LJ. Practical insights into the imaging of odontogenic lesions. In: Farman AG, Ruprecht A, Gibbs SJ, Scarfe WC Advances in Maxillofacial Imaging. Elsevier Science: New York 1997;27-34.         [ Links ]

5. Raitz R, Correa L, Curi MM, Dib LL, Fenyo-Pereira M. Conventional and indirect digital radiographic interpretation of oral unilocular radiolucent lesions. Dentomaxillofac Radiol 2006;35:165-169.         [ Links ]

6. Ikeshima A, Tamura Y. Differential diagnosis between dentigerous cyst and benign tumor with an embedded tooth. J Oral Sci 2002;44:13-17.         [ Links ]

7. Matsumura S, Murakami S, Kakimoto N et al. Histopathologic and radiographic findings of the simple bone cyst. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998;85:619-625.         [ Links ]

8. O’Reilly M, O’Reilly PO, Todd CEC, Altman K, Schfler K. An assessment of the aggressive potential of radiolucencies related to the mandibular molar teeth. Clin Radiol 2000;55:292-295.

9. Yoshiura K, Weber AL, Runnels S, Scrivani SJ. Cystic lesions of the mandible and maxilla. Neuroimaging Clin N Am 2003;13:485-494.         [ Links ]

10. Lipsitz S, Laird NM, Harrington DP. Generalized estimating equations for correlated binary data: using the odds ratio as a measure of association. Biometrika 1991;78:153-160.         [ Links ]

11. Oliveira-Neto HH, Spindula-Filho JV, Dallara MC, Silva CM, Mendonca EF, Batista AC. Unicystic ameloblastoma in a child: a differential diagnosis from the dentigerous cyst and the inflammatory follicular cyst. J Dent Child (Chic). 2007;74:245-249.         [ Links ]

12. Motamedi MH, Ghoreishi M. Management of the simple bone cyst. Dent Today 2008;27:88-90.         [ Links ]

13. McIvor M. The radiological features of odontogenic keratocysts. Br J Oral Surg 1972;10:116-125.         [ Links ]

14. Forssell K, Sorvari TE, Oksala E. A clinical and radiographic study of odontogenic keratocysts in jaws. Proc Finn Dent Soc 1974;70:121-34.         [ Links ]

15. Struthers P, Shear M. Root resorption by ameloblastomas and cysts of the jaws. Int J Oral Surg 1976;5:128-32.         [ Links ]

16. da Silva TA, Batista AC, Mendonca EF, Leles CR, Fukada S, Cunha FQ. Comparative expression of RANK, RANKL, and OPG in keratocystic odontogenic tumors, ameloblastomas, and dentigerous cysts. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;105:333-341.         [ Links ]

17. Copete MA, Kawamata A, Langlais RP. Solitary bone cyst of the jaws: radiographic review of 44 cases. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998;85:221-225.         [ Links ]

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