sign in sign up
<<
Home , Bone, Mandible

ACTA RADIOLÓGICA PORTUGUESA Maio-Agosto 2016 nº 108 Volume XXVIII 25-34

Artigo de Revisão / Review Article

BENIGN MANDIBULAR LESIONS: A PICTORIAL REVIEW LESÕES BENIGNAS DA MANDÍBULA: UMA REVISÃO PICTÓRICA Francisco Rego Costa1, Cátia Esteves1, Maria Teresa Bacelar2

1Serviço de Radiologia do Hospital de São João, Abstract Resumo Porto 2Serviço de Radiologia do Instituto Português de Mandibular lesions are a common imaging fin- As lesões mandibulares constituem um Oncologia, Porto ding and they usually represent a diagnostic achado imagiológico frequente, representando Serviço de Radiologia do Instituto Português de challenge. This article intends to make a pictorial habitualmente um desafio diagnóstico. Este Oncologia do Porto. review of the most frequent benign mandibular artigo pretende realizar uma revisão pictórica Directora: Dra. Margarida Gouvêa lesions categorizing them according to their na- das lesões benignas mais comuns da mandíbula, ture (cystic or ) and also according to their estratificando-as de acordo com a sua natureza origin (odontogenic/non-odontogenic and os- (quística ou sólida) e também de acordo com a seous/non-osseous). Odontogenic lesions will sua origem (odontogénica/não odontogénica Corresponding Author Address be designated accordingly to the World Health e óssea/não óssea). As lesões odontogénicas Organization (WHO) classification of odontoge- serão denominadas tendo por a classificação Francisco Rego Costa nic tumors, published in 2005. da Organização Mundial de Saúde (OMS) dos Serviço de Radiologia The main objectives of this article are to describe tumores odontogénicos, publicada em 2005. Hospital de São João the epidemiologic, anatomic and imaging charac- Os principais objectivos deste artigo são descrever Alameda Prof. Hernâni Monteiro teristics of the most common benign mandibular as características epidemiológicas, anatómicas e 4200–319 Porto lesions, emphasizing the aspects that aid in the imagiológicas das lesões benignas mais comuns e-mail: [email protected] differential diagnosis; and to present some illus- da mandíbula, com ênfase nos aspectos que trative examples of these lesions in orthopanto- permitem realizar o diagnóstico diferencial; e mography, computorized tomography and mag- apresentar alguns exemplos ilustrativos destas Received 21/06/2016 netic resonance. lesões em ortopantomografia, tomografia Acceptance 24/07/2016 computorizada e ressonância magnética. Key-words Palavras-chave Mandibula; Benign lesions; Orthopantomography; Computorized Mandíbula; Lesões benignas; tomography; Magnetic resonance. Ortopantomografia; Tomografia Computorizada; Ressonância Magnética

Introduction Benign Cystic Lesions

Mandibular lesions are relatively common imaging findings. Cystic mandibular lesions are most often odontogenic. They can be encountered by and -dedicated Their anatomic relationship with teeth is an important radiologists or by general radiologists. These lesions can be diagnostic clue. Usually they appear as lucent, well-defined, incidentally detected or actively searched for secondarily to uni or multilocular lesions. Cysts can predispose to infection patient’s symptoms or signs. They usually represent a diagnostic or pathologic fractures1,2. challenge. Knowledge of prevalence, imaging patterns and secondary signs that point to a specific diagnosis are essential Periapical (Radicular) Cyst for a thorough evaluation. Periapical cysts are the most common type of odontogenic Imaging can have a significant impact on treatment, cysts. They are slightly more common in men and have an supporting clinical decisions and avoiding unnecessary and incidence peak between 30 and 60 years. They result from invasive procedures. (PR), computed infectious processes (abscess or granuloma) caused by tomography (CT) and magnetic resonance imaging (MRI) chronic apical periodontitis, usually associated with dental are most useful. The World Health Organization (WHO) cavities1-5. classification of odontogenic tumors, published in 2005, is still PR and CT (Fig. 1) show a lucent unilocular area around used worldwide and will be applied in this article. the root of a non-vital , generally measuring less This article intends to accomplish a pictorial review of the than 1 cm in diameter. Dental root resorption or deviation most common benign mandibular lesions, emphasizing on and cortical expansion are possible complications. MRI anatomical, epidemiological and imaging aspects that are demonstrates lesions with high signal on T2-weighted crucial for narrowing the differential diagnosis. images (T2WI) and only peripheral enhancement. The term residual cyst should be used when referring to a lesion that persists after tooth extraction (Fig. 2)1-3.

25 Figure 3 – Dentigerous cyst. PR shows a lucent image around an unerupted mandibular 3rd (arrow).

appear as well-circumscribed lytic lesions. They commonly affect men aged 50 years or older5,7.

Odontogenic Keratocystic Tumor Odontogenic keratocystic tumors (OKT) are intraosseous benign lesions. Most are localized in the mandibular body or rami. These lesions can induce dental impaction but tooth involvement is not necessary (absent in one third of cases). They are more common in men and have an incidence peak Figure 1 – Periapical cyst. PR (A) shows a lucent rounded image around nd th the root of 4.1 (arrow). The tooth is fragmented. window CT images between the 2 and 4 decades of life. in the coronal (B) and sagittal (C) planes demonstrate a hypodense lesion in Imaging appearance consists of uni or multilocular lesions the mandibular body, surrounding the 4.1 root (white arrows). The tooth is that can extend through “daughter cysts”. The walls of the fragmented and has a cavity (black arrow). lesion are thin but the contour may be lobulated owing to the coalescence of satellite lesions. Osseous expansion and cortical erosion can be evident, especially in large lesions. The internal content is cheese-like in consistency, which is responsible for the CT density as high as 50HU and for the variable signal on MRI T1WI and T2WI (Fig. 4 e 5)3-5,7,8. OKTs can have a locally aggressive behavior and the local recurrence rate after is high (up to 60%). Squamous cell carcinoma malignant transformation is rare3-5,7,8. Basocelular Nevus (Gorlin-Goltz) syndrome should be suspected when multiple lesions are found in a young patient. Other hereditary syndromes such as Ehler-Danlos can be associated with multiple OKTs3-5,7,8. Figure 2 – Residual cyst. Bone window axial CT image shows a well-defined Simple Osseous Cyst hypodense image in the left mandibular body (arrow). Teeth are absent (extracted). Simple osseous cysts are pseudocysts that result from previous traumatic episodes, such as dental extractions, Dentigerous (Folicular) Cyst associated with bone . They are more common in Dentigerous cysts are the second most common type of women and tend to occur before 20 years. These lesions are (after periapical cysts) but are the most commonly located in the posterior mandibular medulla. They 1,4 common developmental (non-acquired) odontogenic cyst. are generally asymptomatic and found incidentally . These lesions form around the of an unerupted tooth Imaging studies demonstrate unilocular radiolucent lesions (usually the 3rd molar). They have an incidence peak at 20-40 of variable dimensions that do not induce erosion nor change years. teeth position. The internal content can be serous, associated PR (Fig. 3) and CT show well-defined unilocular lucent areas with high T2W signal or hemorrhagic, associated with variable around the crown of the 3rd molar (the root of the tooth is spontaneous CT density and MRI signal (that depends on the 1,4 not involved). The tooth follicular space should be greater age of blood). These lesions do not enhance . than 5 mm. Unlike periapical cysts, dentigerous cysts can grow to a large Static Bone Cavity (Stafne Cyst) size and induce teeth deviation and osseous remodeling, Stafne cysts are pseudocysts located in the lingual border although the cortex is usually preserved3,6. CT imaging is of the mandibular angle, caudally to the . important to determine cortical integrity and relationship They result from osseous remodeling due to the adjacent 1,3,4 with adjacent structures (mainly the mandibular canal), prior and are more common in men . to surgical intervention. MRI shows a lesion with signal They are well-defined radiolucent lesions, less than 2 cm in characteristics similar to periapical cysts and is used only in diameter, and represent cortical defects. Imaging evaluation 1,3,4 atypical cases1,3,4. is usually limited to panoramic radiograph .

Periodontal Lateral Cyst These are less common odontogenic cysts. They form between the roots of teeth, usually in the region and

26 Figure 4 – Odontogenic keratocystic tumor. Axial CT images after contrast administration in bone window (A) and soft window (B) display a well-circumscribed lesion in the right mandibular body (arrows) with density, associated with bulging and thinning of the outer cortex, without disruption.

Figure 5 – Odontogenic keratocystic tumor. Bone window axial CT image (A) and PR (B) of the same patient. Image (A) shows a lesion in the transition between the body and the right mandibular ramus (arrow), with soft tissue density, that is responsible for bulging and thinning of the osseous cortex. Image (B) demonstrates a lucent lesion (arrow) adjacent to the roots of the 2nd and 3rd molar, which are intact.

Solid Benign Lesions There are variants that demonstrate metastatic potential while preserving benign histological Odontogenic Tumors characteristics – “malignant ”; and other Odontoma variants that have malignant histological characteristics Odontomas are the most common odontogenic tumors (with or without metastatic potential) – “ameloblastic (approximately 67%). They are hamartomatous lesions carcinomas”1,3,4,10. where a variety of dental components can be identified, Ameloblastomas most commonly arise in the including enamel. They occur more frequently in children (80%), frequently in the posterior body (3rd molar region) and adolescents and have an incidence peak in the 2nd or in the rami. Symptoms are usually non-specific and the decade of life. About half are associated with unerupted 3,9 most common complaint is painless swelling. Most of the teeth and occur around the crown . time the detection is incidental1,3,4,10. The radiographic appearance of odontomas changes with Four types of ameloblastoma exist: multicystic (Fig. 8 and time. Initially these lesions are radiolucent but tend to 9), unicystic (Fig. 10), extraosseous and desmoplastic. The progressively calcify until they become radiopaque. In the multicystic type is the most frequent (85% of tumors) and last stages the margins are well defined, usually surrounded 3,9 also the most aggressive. The imaging appearance varies by a lucent halo. They can deviate and erode teeth . with the histologic type but their differentiation based solely The WHO classification comprises two types of on imaging patterns is not possible. The multicystic type is odontomas: compound (Fig. 6), occurring more commonly generally a multilocular lucent lesion (“soap bubble-like”) in the anterior and demonstrating some dental and can display thick septa, solid components or papillary components (denticles); and complex (Fig. 7), that normally projections that enhance after contrast administration. The occur in the molar region of the mandible, showing only 3,9 desmoplastic type is noticeable for the presence of coarse amorphous . calcifications1,4,7,10. Ameloblastoma Locally aggressive behavior is demonstrated by dental root Ameloblastomas constitute 10% of odontogenic tumors erosion and significant osseous expansion. CT and MRI are and originate in the enamel-producing epithelial cells. They important to evaluate for malignant degeneration, cortical are equally common in both genders and have an incidence rd th integrity, extension of osseous and soft tissue involvement peak between the 3 and 5 decades of life. These are and relationship with the mandibular canal. MRI shows classically benign, slow-growing tumors but locally lesions with low signal on T1WI and high signal on aggressive1,3,4,10.

Figure 6 – Compound odontoma. PR (A) and bone window axial CT image (B) of the same patient disclose a sclerotic lesion in the left mandibular body/ramus transition (arrows), around the root of 3.6. In (B) some peripheral odontogenic elements are discernible (arrowheads) that point toward a diagnosis of compound odontoma (although not in the classical location).

27 Figure 7 – Complex odontoma. PR (A) and bone window axial CT image (B) of the same patient demonstrate a sclerotic lesion in the right mandibular ramus (arrows) adjacent to the crown of an unerupted tooth. Only amorphous tissue is visible, without evidence of odontogenic elements..

Figure 8 – Multicystic ameloblastoma. PRs (A and B) show multilocular lucent lesions (arrows) demonstrating the classic “soap bubble-like” pattern.

Figure 9 – Multicystic ameloblastoma. Soft-tissue window axial CT image (A) shows a bilocular lesion in the right mandibular body (arrow) demonstrating cortical disruption anteriorly, where an enhancing septum is visible (arrowhead). Bone window sagittal CT image (B) showing a lucent lesion in the right mandibular body/ ramus transition, with osseous expansion, cortical disruption and fine septa (arrow).

Figure 10 – Unicystic ameloblastoma. PR (A) presents a unilocular lucent lesion in the right mandibular body (arrow). A barely visible fine septum is discernible (arrowhead). Bone window axial CT image (B) of the same patient shows a unilocular lucent lesion (arrow) with osseous expansion and anterior cortical disruption (arrowhead).

T2WI. Positron emission tomography in conjunction with roots of the anterior mandible, usually in the region of the CT (PET/CT) shows benefit in detection of malignant canines. They affect preferentially African or Asian women variants1,4,7,10. and have an incidence peak during the 4th and 5th decades Cementoblastoma of life3,9. Cementoblastomas are rare benign tumors (less than 1% The initial imaging appearance is a lucent periapical lesion of odontogenic tumors). They commonly occur in the pre- that tends to become more opaque with time, turning molar or molar regions of the mandible and are usually into a sclerotic well-marginated lesion (Fig. 11). Unlike periapical. The majority of patients are younger than 25 cementoblastomas they are not prone to fuse with teeth years, and these tumors occur more frequently in men1-3,9. roots. A diffuse form, affecting two or more maxillary The most common imaging pattern is a sclerotic periapical quadrants, is called florid cemento-osseous dysplasia3,9. rounded lesion that tends to fuse with the tooth root and Ameloblastic Fibroma possibly invade the tooth root canal1-3,9. Ameloblastic fibromas are rare lesions affecting primarily Cemento-Osseous unerupted teeth in the posterior mandible. Their aspect Cemento-osseous dysplasia originates from a connective is similar to unilocular ameloblastomas and entails lucent tissue proliferation of the periodontal membrane. These pericoronal well-defined lesions (Fig. 12)3,11. lesions are frequently multifocal and occur among tooth

28 Figure 11 – Cemento-osseous dysplasia. Bone window axial (A) and coronal (B) CT images demonstrate a focal sclerotic well- defined lesion in the left mandibular body (arrows), without osseous expansion.

Figure 12 – Ameloblastic fibroma. Bone window coronal (A) and sagittal (B) CT images disclose a lucent pericoronal lesion abutting the unerupted 3rd molar of the left mandible (arrows).

Condensing fibromas, sometimes associated with a radiolucent border, Condensing osteitis is a periapical reactive osteitis, is useful in this distinction3,4,9,13. usually secondary to an inflammatory process (pulpitis) Fibrous Dysplasia and associated with other inflammatory lesions such as Fibrous dysplasia is a congenital defect in the differentiation granulomas, cysts or abscesses. Children and young adults and maturation of that induces normal bone are usually affected and the lesions predominate in the transformation into fibrous stroma and immature bone. premolar or molar regions of the mandible. Craniofacial fibrous dysplasia commonly affects young On imaging they feature as sclerotic, ill-defined and non- adults and is usually monostotic. Craniofacial are expansible lesions, adjacent to a non-vital tooth9,12. involved in about half the cases of polyostotic fibrous dysplasia. Mandible involvement is possible although not Osseous Non-Odontogenic Tumors very common. These lesions grow along the longitudinal Ossifying Fibroma of the involved bone, which they expand. They are Ossifying fibromas are composed of fibrous tissue and less focal lesions than ossifying fibromas. Typically fibrous variable amounts of osseous trabeculae. There are several dysplasia becomes quiescent in adults but some growth can subtypes including cementifying, cemento-ossifying and be seen in this age group9,14. juvenile. Most of these tumors occur in the posterior On imaging they display heterogeneous ground glass mandible (premolar and molar regions). They are more and show a wide and ill-defined transition zone, common in women and have an incidence peak during the a feature that is useful to distinguish them from ossifying 3rd and 4th decades of life3,4,9,13. fibromas. The bony cortex is commonly thickened but not The main radiographic characteristic is ground glass disrupted and teeth dislocation is not usual (Fig. 14 and attenuation. Their appearance can change over time from 15)9,14. radiolucent to radiopaque or mixed lesions. Usually they are MRI shows lesions of variable signal intensity that is unilocular and locally expansive. Dislocation and erosion of influenced by the degree of lucency vs. ground glass teeth are frequent (Fig. 13)3,4,9,13. attenuation that they possess. On T1WI lesions demonstrate The most important differential diagnosis is fibrous low to intermediate signal (Fig. 14C). On T2WI lesions dysplasia. The narrow zone of transition typical of ossifying

Figure 13 – Ossifying fibroma. Bone window axial CT images (A and B) show two unifocal and expansive lesions with ground glass attenuation (arrows) in the right mandibular body (A) and in the right mandibular ramus (B). Both lesions demonstrate a narrow transition zone and in (B) a radiolucent border is visible (arrowheads).

29 Figure 14 – Monostotic fibrous dysplasia. PR (A) and bone window axial CT image (B) demonstrate an expansible and homogeneous lesion with ground glass attenuation in the right mandibular ramus (arrows). There is an ill-defined transition zone but the lesion does not erode adjacent teeth. Axial MR T1WI (C), T2WI (D) and T1WI after gadolinium (E) demonstrate low T1 signal, areas of high T2 signal and heterogeneous enhancement (arrows).

Fig. 15 – Monostotic fibrous dysplasia. PR (A) and bone window axial CT image (B) show an expansible lesion with heterogeneous ground glass attenuation (arrows) in the left mandibular body. CT tridimensional image after volumetric reconstruction (volume-rendered) illustrates the predominant growth of these lesions along the longitudinal axis (arrows).

are usually hypointense although they can show some pathognomonic (Fig. 17). Lesions can be solitary or focal areas of hyperintensity (Fig. 14D). After gadolinium multiple, the latter being related to the autosomal dominant administration there is a strong and heterogeneous syndrome named hereditary multiple exostoses. Malignant enhancement (Fig. 14E)9,14. transformation occurs in about 1% of solitary and 3-5% of Idiopathic Osteosclerosis multiple hereditary osteochondromas7,9,16. Idiopathic osteosclerosis is an osseous developmental Imaging features that are associated with malignancy variant of unknown cause and not related to local stimuli. include continuous growth and thick cartilaginous cap In 90% of cases it occurs in the mandible (usually in the (>1,5 cm) after skeletal maturity7,9,16. premolar or molar regions) and is frequently asymptomatic. A peak incidence occurs between the 1st and 2nd decades Approximately 15-37% of patients treated with of life. There is a uniform distribution in both genders9,15. for tumors in the head and neck region Radiograph and CT demonstrate sclerotic, focal and experience osseous necrosis, secondary to hypoxia and rounded lesions, well marginated and usually periapical hypovascularization caused by radiation. These events (80% of cases) (Fig. 16). Spiculated margins can be seen. lead to cell death and . Osteoradionecrosis is dose- They can grow slowly until skeletal maturation is complete dependent and more common with radiation doses above but do not induce osseous expansion. Sometimes they are 60 Gy. Evidence of bone necrosis can arise months or multifocal9,15. years (usually between 5-15 years) after the conclusion of radiation therapy. The mandible is more susceptible than are the most common bone tumors. the maxilla and the vestibular cortex is more vulnerable They are composed of cortical and medullary bone and than the lingual cortex. The body of the mandible is most covered by a hyaline cartilaginous cap. Continuity with frequently affected (around the molar region). The and the parent cortical bone and medullary canal is considered mandibular angles are usually spared3,4,9. 30 Figure 16 – Idiopathic osteosclerosis. Bone window axial CT images (A and B) of the same patient show two sclerotic and spiculated lesions (arrows) in the right mandibular body (A) and in the center of the mandibular body (B). There is no osseous expansion or lucent halo.

Figure 17 – Osteochondroma. Bone window axial, coronal and sagittal CT images (A, B and C) of the same patient demonstrate an exophytic lesion in the right mandibular ramus (arrows) continuous with the parent bone. In (C) the cartilaginous cap is visible as a thin hypodense peripheral layer (arrowhead).

Osteoradionecrosis features on CT as an ill-defined area of mixed attenuation (lytic and sclerotic foci), loss of normal Osteomyelitis is a bone infection (usually bacterial) with bone trabeculation, cortical disruption, fragmentation and medullary involvement. It is rare in healthy subjects due to bony (Fig. 18). Soft tissue masses and periosteal antibiotic treatment. The mandible is commonly affected reaction are characteristically absent, findings that are useful (more than the maxilla). Most patients have dental cavities or is the differential with tumor relapse. previous dental extractions. Mandibular or dental fractures MRI shows areas of bone edema and sclerosis with and osteonecrosis are other possible predisposing factors. heterogeneous enhancement. Diffusion weighted images Chronic osteomyelitis (>1 month) may have complications (DWI) are useful in the differentiation with tumor relapse such as sinus tracts, fistulae, bone sequestra or pathologic (low ADC values) from osteoradionecrosis (high ADC fractures. The most common risk factors are diabetes values)3,4,9. mellitus, alcoholism, malnutrition, radiation therapy and -related Osteoradionecrosis bisphosphonate treatment3,4,9. are frequently used in oncologic patients Common imaging findings consist of focal disturbance and improve their quality of life. The benefits result from of bone trabeculation with mixed attenuation (lytic and osteoclastic activity inhibition and consequent reduction in opaque areas), cortical disruption, bone sequestra, gas the growth of bone lesions and prevention of pathologic attenuation and (Fig. 20). CT is useful fractures. This can also be used in non-oncologic to define the extension and severity of bone and soft tissue diseases, such as . A potential side effect of involvement (abscesses, myositis, fasciitis or cellulitis). MRI this treatment is bone necrosis. Bisphosphonate-related shows greater sensivity in the detection of osteomyelitis, osteonecrosis occurs preferentially in the mandible (more allowing earlier diagnosis. This entity demonstrates low than in the maxilla), usually in the molar region. Focal signal intensity on T1WI, high signal on liquid-sensitive lesions and traumatic events (such as dental extractions) sequences and enhancement of adjacent soft tissues. Bone can facilitate4,9. sequestra show marked hypointensity on all sequences3,4,9. Imaging features are similar to osteoradionecrosis. Clinical factors are very important in the differential diagnosis that implies absence of previous radiotherapy4,9. 31 Figure 18 – Osteoradionecrosis. PR (A) and bone window axial CT images (B and C) show the classic features of this entity (arrows), disclosed by an ill-defined lytic area with bone destruction, cortical disruption and sequestrum (arrowheads).

Figure 19 – Bisphosphonate- related osteonecrosis. Bone window axial CT image of a patient with mandibular osteonecrosis after bisphosphonate treatment demonstrates several lytic areas (arrows) and a bone sequestrum (arrowhead). Figure 20 – Osteomyelitis. Bone window axial and coronal CT images (A and B) of a patient with a history of right partial pelviglossectomy demonstrate cortical thinning and gas attenuation in the right mandibular ramus (arrows), with associated cutaneous fistula (arrowheads). These findings are indicative of chronic osteomyelitis.

Non-Odontogenic Non-Osseous Tumors Typical imaging characteristics consist of well-defined Giant Cell Granuloma lucent and multilocular lesions (honeycomb-like) (Fig. Giant cell granulomas are composed of fibrous and 21). Thin bone septa can be discernible. Lesions can also hemorrhagic tissue as well as giant osteoclastic cells. They be unilocular (particularly in an early stage) or present are rare, benign but locally aggressive tumors. Children and ill-defined borders. Sometimes there is bone expansion, young adults are most affected, especially women. They teeth depositioning or erosion and cortical disruption. On have an incidence peak in the 2nd and 3rd decades of life. MRI lesions show homogeneous intermediate signal on These lesions tend to occur in the posterior mandible3,4. T1WI and T2WI and moderate/marked enhancement.

32 Figure 21 – Giant cell granuloma. PR (A) and bone window sagittal CT image (B) demonstrate a lucent multilocular lesion in the right mandibular body (arrows). Note the idiopathic osteosclerosis adjacent to the root of 4.7 (arrowheads).

Brown tumors from hyperparathyroidism are an important Sheath Tumors differential diagnosis and denote identical imaging and Nerve sheath tumors are benign and slow-growing lesions. pathologic features. Laboratory studies usually allow They are rare tumors that show preference for the head and distinction3,4. neck region. The mandible is the most commonly affected Eosinophilic Granuloma bone, usually in the ramus or posterior body. These lesions Eosinophilic granulomas are benign osseous lesions that are more frequent in women and have an incidence peak represent the focal demonstration of a systemic disease between the 3rd and 4th decades of life18. named Histiocytosis (LCH). LCH is a Radiographs show lucent uni or multilocular lesions. Erosion disease caused by the clonal proliferation of dendritic cells of the adjacent teeth roots is frequent and enlargement of and . Manifestations can be unifocal, multifocal the mandibular canal or may be the only but uni-system or multifocal and multi-system. About 7% findings. On CT they present as homogeneous masses of of cases occur in the mandible (usually in the body or the soft tissue density, sometimes with septa. MRI generally mandibular angle) but any bone can be affected. These demonstrates high signal in liquid-sensitive sequences lesions are more common in men and have an incidence and enhancement after gadolinium administration (more peak between the 1st and 3rd decades of life4,17. striking in schwannomas) (Fig. 23). A central hypointense Imaging reveals a lucent lesion generally associated with area surrounded by a hyperintense ring (“target sign”) is periosteal reaction (that may show a “sunburst” pattern) (Fig. more frequent in neurofibromas (although not exclusive)18. 22). When the teeth arcade is involved, osseous destruction The relationship of the tumor with the inferior alveolar may induce a characteristic “floating tooth” appearance. nerve is determinant. Neurofibromas tend to grow Associated soft tissue masses around the mandible and along the mandibular canal and have an ovoid shape. are frequent. On MRI these Schwannomas rarely grow inside the canal, having a more lesions demonstrate low signal on T1WI and high signal rounded morphology18. on T2WI. Marked enhancement and surrounding edema are typical. ADC values are usually higher than malignant lesions. is crucial for a definitive diagnosis. PET/ CT and PET/MR are useful in the detection of lesions in multifocal and multi-system disease and also in treatment monitoring4,17.

Figure 22 – Eosinophilic Granuloma. Bone window axial (A) and sagittal (B) CT images demonstrate several lytic focuses in the mandibular body (arrows), with associated cortical disruption and bone sclerosis, regarding multifocal disease. Volumetric reconstruction image (C) demonstrates bone destruction caused by the lesions.

33 Figure 23 – schwannoma. MR axial T2WI (A), T1WI (B) and T1WI -saturated post-contrast (C) show a lobulated lesion that arises from the medial right mandibular ramus (where the mandibular canal originates) and extends to the right masticator space (arrows). The lesions has heterogeneous high signal on T2WI (A) and intense enhancement (C).

Conclusion essential for radiologic evaluation. The accurate diagnosis of these lesions is clinically useful because it can guide the Knowledge of the more important epidemiologic and therapeutic approach and follow-up, avoiding unnecessary imaging characteristics of the benign mandibular lesions is procedures.

References 10. Sham E, Leong J, Maher R, Schenberg M, Leung M, Mansour AK. 1. Devenney-Cakir B, Subramaniam RM, Reddy SM, Imsande H, Gohel A, Mandibular Ameloblastoma: Clinical Experience and Literature Review. Sakai O. Cystic and Cystic-appearing Lesions of the Mandible: Review. AJR ANZ J Surg. 2009;79:739–44. Am J Roentgenol. 2011 Jun;196(6 Suppl):WS66-77. 11. Zallen RD, Preskar MH, McClary SA. Ameloblastic Fibroma. J Oral 2. Weber AL, Kaneda T, Scrivani SJ, Aziz S. . Cysts, Tumors and Maxillofac Surg. 1982;40(8):513–17. Nontumorous Lesions. In: Som PM, Curtin HD, eds. Head and neck 12. Abrahams JJ, Berger SB. Inflammatory Disease of the Jaw: Appearance imaging, 4th ed. St. Louis, MO: Mosby, 2003:930–94. on Reformatted CT scans. AJR Am J Roentgenol. 1998;170(4):1085–91. 3. Dunfee BL, Sakay O, Pistey R, Gohel A. Radiologic and Pathologic 13. Eversole R, Su L, ElMofty S. Benign Fibro-Osseous Lesions of the Characteristics of Benign and Malignant Lesions of the Mandible. Craniofacial Complex: A Review. Head Neck Pathol. 2008;2(3):177–202. Radiographics. 2006 Nov-Dec;26(6):1751-68. 14. MacDonald-Jankowski DS. Fibro-Osseous Lesions of the and . 4. Avril L, Lombardi T, Ailianou A, Burkhardt K, Varoquaux A, Scolozzi P, Clin Radiol. 2004;59(1):11–25. Becker M. Radiolucent Lesions of the Mandible: A Pattern-Based Approach 15. Yonetsu K,Yuasa K, Kanda S. Idiopathic Osteosclerosis of the Jaws: to Diagnosis. Insights Imaging. 2014 Feb;5(1):85-101. Panoramic Radiographic and Computed Tomographic Findings. Oral Surg 5. White SC, Pharoha MJ. Cysts and Cystlike Lesions of the Jaws. In: White Oral Med Oral Pathol Oral Radiol Endod. 1997;83(4):517–21. SC, Pharoha MJ, eds. Oral : principles and interpretation, 6th ed. St. 16. Murphey MD, Choi JJ, Kransdorf MJ, Flemming DJ, Gannon FH. Louis, MO: Mosby Elsevier, 2009:343–65. Imaging of Osteochondroma: Variants and Complications with Radiologic- 6. Freitas DQ, Tempest LM, Sicoli E, Lopes-Neto FC. Bilateral Dentigerous Pathologic Correlation. Radiographics. 2000;20(5):1407-34. Cysts: Review of the Literature and Report of An Unusual Case. 17. Mueller WP, Melzer HI, Schmid I, Coppenrath E, Bartenstein P, Pfluger Dentomaxillofac Radiol. 2006; 35:464–68. T. The Diagnostic Value of 18F-FDG PET and MRI in Paediatric 7. Meyer KA, Bancroft LW, Dietrich TJ, Kransdorf MJ, Peterson JJ. Imaging Histiocytosis. Eur J Nucl Med Mol Imaging. 2013;40:356–63. Characteristics of Benign, Malignant, and Infectious Jaw Lesions: a Pictorial 18. Nakasato T, Katoh K, Ehara S, Tamakawa Y, Hoshino M, Izumizawa Review. AJR Am J Roentgenol. 2011 Sep;197(3):W412-21. M, Sakamaki K, Fukuta Y, Kudoh K. Intraosseous Neurilemmoma of the 8. Shear M. Odontogenic Keratocysts: Natural History and Mandible. AJNR Am J Neuroradiol. 2000 Nov-Dec;21(10):1945-7. Immunohistochemistry. Oral Maxillofac Surg Clin N Am. 2003;15:347–62. 9. Curé JK, Vattoth S, Shah R. Radiopaque Jaw Lesions: An Approach to the Differential Diagnosis. Radiographics. 2012 Nov-Dec;32(7):1909-25.

34