DOI: 10.1148/rg.266055189
RadioGraphics 2006;26:1751-1768
© RSNA, 2006
Radiologic and Pathologic Characteristics of Benign and Malignant Lesions of the Mandible1
Brian L. Dunfee, MD,
Osamu Sakai, MD, PhD,
Robert Pistey, MD and
Anita Gohel, BDS, PhD
1 From the Departments of Radiology (B.L.D., O.S.) and Pathology (R.P.), Boston University School of Medicine, Boston Medical Center, 715 Albany St, Boston, MA 02118; and the Department of Diagnostic Sciences and Pathology, Boston University Goldman School of Dental Medicine, Boston, Mass (A.G.). Recipient of a Certificate of Merit award for an education exhibit at the 2004 RSNA Annual Meeting. Received October 19, 2005; revision requested March 7, 2006 and received May 30; accepted May 31. All authors have no financial relationships to disclose.
Address correspondence to B.L.D. (e-mail: Brian.Dunfee{at}bmc.org).
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Abstract
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Mandibular lesions develop from both odontogenic and nonodontogenic origins and have varying degrees of destructive potential. Common benign cystic lesions include periapical (radicular) cysts, follicular (dentigerous) cysts, and odontogenic keratocysts. Benign solid tumors represent a broad spectrum of lesions such as ameloblastomas, odontomas, ossifying fibromas, and periapical cemental dysplasia. Malignant tumors that often involve the mandible include squamous cell carcinomas, osteosarcomas, and metastatic tumors. In addition, vascular lesions such as hemangiomas and arteriovenous malformations may develop, further expanding the differential diagnosis. Because mandibular lesions have a wide range of pathologic features but similar imaging appearances, familiarity with embryologic characteristics and secondary findings is crucial. Patient age at manifestation, prevalence, location within the mandible, cystic or solid appearance, border contour, and effect of the lesion on adjacent structures are all considerations in making the diagnosis. Despite this information, however, many lesions are impossible to differentiate without biopsy. In such cases, defining the degree of malignant potential is very helpful. Although imaging will not always provide a specific diagnosis, it should help narrow the differential diagnosis, thereby helping to guide patient treatment.
© RSNA, 2006
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LEARNING OBJECTIVES FOR TEST 4
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After reading this article and taking the test, the reader will be able to:- Discuss the differential diagnosis for various mandibular lesions based on their demographic characteristics, location, and morphologic features.
- Describe the clinical and imaging features of specific benign and malignant mandibular lesions.
- Identify specific imaging features of mandibular lesions that should prompt tissue biopsy for a more definitive diagnosis.
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Introduction
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A variety of benign and malignant lesions occur within the mandible. Although the radiologic findings in some mandibular lesions may be non-specific, there are often clues for histologic diagnosis within the anatomy surrounding each lesion. In many cases, the clinical history alone is crucial in reaching a correct diagnosis. Precise radiologic evaluation of a lesion can have a significant impact on diagnosis and subsequent patient treatment.
The World Health Organization (WHO) classification scheme published in 1992 classifies mandibular lesions as benign or malignant, with further subdivisions based on the predominant odontogenic tissue involved (Table 1) (1). In this article, we briefly review the process of odontogenesis. We also discuss and illustrate the radiologic and, in some cases, pathologic findings in various cystic lesions, solid benign and malignant lesions, infectious lesions, vascular and neurogenic lesions, metabolic processes, and tumorlike lesions (Table 2). In addition, we discuss the location (Table 3) and prevalence (Table 4–6) of various mandibular lesions to aid in narrowing the differential diagnosis.
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Odontogenesis
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The first brachial arch forms the mandible during the fourth week of embryologic development by means of fusion of the bilateral mandibular prominences. These structures eventually give rise to the teeth through a process called odontogenesis. Each tooth develops from (a) ectodermal cells that develop into ameloblasts and other outer tooth regions, and (b) ectomesenchymal cells that form the odontoblasts and dental papillae. This process begins at the crown of the tooth and continues toward the root (2).
Four stages of odontogenesis have been described, including the bud, cap, bell, and crown (apposition) stages (3). During the sixth week of embryonic development, mesenchymal cells thicken and form the primary dental lamina. These cells begin to invaginate to form a tooth bud with an overlying cap. By the 20th week, the tooth bud appears bell shaped with active ameloblastic and odontoblastic cells. Ameloblastic cells produce tooth enamel, whereas odontoblastic cells form the dentin. The production of enamel requires the complete formation of the underlying dentin. Both of these processes are completed during the crown stage, as the tooth enters the final stage of development.
Prior to completion of odontogenesis, both the primary and secondary dental laminae disappear. Any remnants of these embryonic cells may give rise to both benign and malignant lesions later in life. The remaining ectomesenchymal cells surrounding a tooth create the dental sac, which contains the periodontal ligament and cementum. The periodontal ligament is a thin fibrous ligament that attaches the cementum of each tooth to the surrounding alveolar bone (lamina dura). This highly vascularized connective tissue allows limited motion of each tooth during mastication and also serves to provide sensation. Secured to the mandible by these components, the teeth migrate into the oral cavity, and the developmental process is complete (Fig 1) (2).
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Figure 1a. Odontogenesis and tooth anatomy. (a) Drawings illustrate the major stages of tooth development: the bud stage, cap stage, bell stage, and crown stage. Pink = oral epithelium, brown = dental mesenchyme, dark blue = ameloblasts, light blue = odontoblasts, yellow = dentin, white = enamel, red = pulp. Although mandibular lesions may originate from cells of early tooth development, they often do not manifest until later in life. (b) Radiograph demonstrates the anatomy of a mature tooth. Lesions of the mandible typically arise from characteristic locations within and surrounding a tooth.
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Figure 1b. Odontogenesis and tooth anatomy. (a) Drawings illustrate the major stages of tooth development: the bud stage, cap stage, bell stage, and crown stage. Pink = oral epithelium, brown = dental mesenchyme, dark blue = ameloblasts, light blue = odontoblasts, yellow = dentin, white = enamel, red = pulp. Although mandibular lesions may originate from cells of early tooth development, they often do not manifest until later in life. (b) Radiograph demonstrates the anatomy of a mature tooth. Lesions of the mandible typically arise from characteristic locations within and surrounding a tooth.
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Cystic Lesions
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A true mandibular cyst forms when developmental or inflammatory factors stimulate proliferation of epithelial cells surrounding a tooth. As these cells grow, the central cells become removed from their nutrient supplied by adjacent vascular connective tissue and become necrotic. Subsequently, an epithelium-lined cavity or sac is formed (2).
Mandibular cysts appear radiologically as well-defined lucent areas within the bone. Although most cysts have a sclerotic rim, severe underlying inflammation may result in a decreased degree of sclerosis. Cysts are classified according to the cell of origin, with the majority of cysts in the jaw arising from odontogenic sources (2). However, cysts may also arise from prior trauma or surgery. The wide range in the frequency with which various cystic lesions occur often helps narrow the differential diagnosis (Table 4).
Periapical (Radicular) Cyst
The periapical (radicular) cyst is the most common odontogenic cyst and results from inflammation secondary to caries or other entities. The peak prevalence of this asymptomatic cyst occurs between the fourth and sixth decades of life. Typically, infection spreads to the apex (root) of the tooth, leading to secondary apical periodontitis, granuloma, or abscess and, finally, cyst formation. The cyst appears as a round or pear-shaped, well-defined radiolucent lesion with sclerotic borders. Most periapical cysts are less than 1 cm in diameter (4). It is important to note that radiology cannot always help distinguish a granuloma from a cyst (Figs 2, 3) (1,2).
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Figure 2a. Periapical cyst in a 60-year-old woman. Computed tomographic (CT) scan (a) and coronal reformatted CT image (b) demonstrate a radiolucent lesion (arrows) surrounding the apex of a molar. A defect with dental filling (arrowhead) is present within the crown of the tooth.
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Figure 2b. Periapical cyst in a 60-year-old woman. Computed tomographic (CT) scan (a) and coronal reformatted CT image (b) demonstrate a radiolucent lesion (arrows) surrounding the apex of a molar. A defect with dental filling (arrowhead) is present within the crown of the tooth.
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Figure 3. Periapical cyst in a 40-year-old man. Panorex image demonstrates a circular radiolucent lesion (arrow) at the apex of a molar. Note the dental filling (arrowhead) from a prior procedure.
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Follicular (Dentigerous) Cyst
Follicular (dentigerous) cyst is the most common developmental odontogenic cyst. The lesion forms around the crown of an unerupted tooth (commonly the third molar) and is typically diagnosed in patients between 30 and 40 years of age. The enamel epithelium surrounding the crown proliferates, and fluid collects between the layers. Therefore, identifying the crown of a tooth projecting into the cystic cavity is pathognomonic (2). The cyst appears radiologically as a well-demarcated radiolucent lesion attached at an acute angle to the cervical area of an unerupted tooth. The border of the lesion may be radiopaque (5).
Unlike radicular cysts, a follicular cyst may become extremely large, often distorting the roots of adjacent teeth and remodeling the mandible. However, the cortical bone is usually preserved (Fig 4). A few cases of ameloblastic transformation of a follicular cyst in patients under 40 years of age have been reported (3).
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Figure 4. Follicular cyst in a 40-year-old man. Coronal reformatted CT image reveals a cystic lesion with an unerupted tooth in the right molar region (arrow). The crown of the tooth is contained within the lesion. Note the presence of bone remodeling rather than expansion.
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Odontogenic Keratocyst
OKCs are most commonly located in the body or ramus of the mandible. Most OKCs possess destructive potential, with a high recurrence rate after resection (3). OKCs develop from the dental lamina, which is found throughout the jaw and overlying alveolar mucosa and is lined by stratified keratinizing squamous epithelium. Thus, the cysts can occur throughout periapical or primordial regions. Unlike follicular cysts, OKCs can expand cortical bone and erode the cortex (2). Fortunately, malignant transformation of these lesions is rare. The lesion is multiloculated, often with daughter cysts that extend to the surrounding bone (Figs 5, 6). Multiple OKCs in a young patient should raise the possibility of basal cell nevus syndrome (Gorlin-Goltz syndrome). Associated findings with this autosomal dominant disorder include midface hypoplasia, frontal bossing and prognathism, mental retardation, and calcification of the falx cerebri (Fig 6) (2).
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Figure 5. OKCs in a 22-year-old man. Panoramic reformatted CT image demonstrates cystic lesions with well-demarcated borders (arrows) within the mandible. There is no evidence of adjacent tooth root erosion. Note the slight expansile change and remodeling of the mandibular cortex without bone destruction.
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Figure 6. OKC in a 41-year-old man with basal cell nevus syndrome (Gorlin-Goltz syndrome). Contrast material–enhanced CT scan shows multiple cysts (arrows) in the mandible. Cystic lesions (arrowheads) are also identified within the maxilla. CT also demonstrated a calcified falx and large frontal sinuses, findings that helped establish the diagnosis.
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Primordial Cyst
A less common cystic lesion is the primordial cyst, which develops instead of a tooth. It is believed that the dental follicle forms but subsequently undergoes cystic degeneration before completion of odontogenesis. The nonexpansile lesion is well defined and radiolucent, without an associated tooth (3).
Residual Cyst
Residual cyst is a generic term for any cyst that remains after surgical intervention. Thus, most residual cysts are periapical (radicular) cysts (3).
Static Bone Cavity (Stafne Cyst)
A static bone cavity appears as an ovoid or round, well-defined radiolucent lesion within a cortical defect on the medial surface of the posterior mandible (3). Typically measuring less than 2 cm, the cavity of this pseudocyst is usually filled with fat but may also contain submandibular salivary gland tissue (Fig 7) (5).
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Figure 7. Static bone cavity (Stafne cyst) in a 35-year-old man. CT scan reveals a cortical defect (arrow) in the lingual surface of the right mandibular angle, a finding that does not represent a true cyst.
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Solitary Bone Cyst (Traumatic, Simple, Hemorrhagic Bone Cyst)
A solitary bone cyst results from trauma, which leads to intramedullary hemorrhage and subsequent resorption. These pseudocysts are most commonly located in the posterior marrow space of the mandible and appear slightly irregular with poorly defined borders. They have a characteristic scalloped superior margin extending between the roots of adjacent teeth. In addition, the mandibular cortex may be thinned secondary to osseous expansion (Fig 8) (3).
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Figure 8. Solitary (hemorrhagic) bone cyst in a 25-year-old woman. Coronal reformatted CT image demonstrates a cystic lesion (arrows) within the mandibular body. The mandibular cortex is thinned. Note the normal tooth (arrowhead) within the lesion, a finding that helps distinguish the cyst from radicular or other odontogenic cysts.
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Solid Benign Lesions
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Primary Odontogenic Tumors
Odontoma.—
Odontoma is the most common odontogenic tumor of the mandible, accounting for approximately 67% of all cases (6). The lesion consists of various tooth components, including dentin and enamel, which have developed abnormally to form a "hamartomatous" lesion. Nearly 50% of odontomas are associated with an impacted tooth, and most are diagnosed during the second decade of life. However, odontomas may develop before or after tooth eruption (3).
Forming between the roots of teeth, the tumor is initially radiolucent but evolves to contain small calcifications. Eventually, the tumor forms a radiopaque mass with a lucent rim. The WHO classification scheme further subdivides odontomas into compound and complex types, depending on their composition compared with normal teeth (1). Compound odontomas have radiographically identifiable tooth components (abortive teeth), whereas complex odontomas contain multiple masses of dental tissue with amorphous calcifications. Most odontomas can cause impaction or resorption of adjacent teeth (Fig 9) (2,3).
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Figure 9. Compound odontoma in a 28-year-old woman. Panorex image demonstrates a focus of radiopaque enamel surrounded by a thin radiolucent follicle (arrow). Note the impacted tooth (arrowheads) deep to the odontoma.
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Ameloblastoma.—
Ameloblastoma arises from the enamel-forming cells of the odontogenic epithelium that have failed to regress during embryonic development. The tumor most commonly occurs in the posterior mandible, typically in the third molar region, with associated follicular cysts or impacted teeth. The slow growth of the tumor can lead to significant expansion of the mandible. Patients typically present in the third to fifth decades of life with a slow-growing, painless mass. The expansile, radiolucent tumor can be unilocular or multilocular, with a characteristic "soap bubble–like" appearance. CT findings include cystic areas of low attenuation with scattered isoattenuating regions, representative of soft-tissue components. The lesion can also erode through the cortex with extension into the surrounding oral mucosa. In addition, erosion of the roots of adjacent teeth is unique to ameloblastoma and indicates the aggressive behavior of the tumor (2). However, only histopathologic findings can help determine benignity and the absence of carcinomatous change (Fig 10) (2,7).
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Figure 10a. Ameloblastoma in a 20-year-old man. (a) CT scan demonstrates a multiloculated cystic lesion (arrow) within the left mandible. The crown of an impacted tooth (arrowhead) identified within the lesion is a clue to the diagnosis. (b) Photograph shows a soft-tissue mass in the resected mandible. (c) High-power photomicrograph (hematoxylin-eosin [H-E] stain) reveals numerous well-defined islands of odontogenic epithelium with palisading and polarizing nuclei (arrows).
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Figure 10b. Ameloblastoma in a 20-year-old man. (a) CT scan demonstrates a multiloculated cystic lesion (arrow) within the left mandible. The crown of an impacted tooth (arrowhead) identified within the lesion is a clue to the diagnosis. (b) Photograph shows a soft-tissue mass in the resected mandible. (c) High-power photomicrograph (hematoxylin-eosin [H-E] stain) reveals numerous well-defined islands of odontogenic epithelium with palisading and polarizing nuclei (arrows).
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Figure 10c. Ameloblastoma in a 20-year-old man. (a) CT scan demonstrates a multiloculated cystic lesion (arrow) within the left mandible. The crown of an impacted tooth (arrowhead) identified within the lesion is a clue to the diagnosis. (b) Photograph shows a soft-tissue mass in the resected mandible. (c) High-power photomicrograph (hematoxylin-eosin [H-E] stain) reveals numerous well-defined islands of odontogenic epithelium with palisading and polarizing nuclei (arrows).
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Although multiple subtypes of ameloblastomas exist, most cannot be distinguished with radiology alone. Histopathologic analysis must provide the definitive subtype diagnosis of each lesion, with the exception of desmoplastic ameloblastoma. Distinguishing features of this subtype include multiple coarse internal calcifications with significant surrounding cortical destruction (Fig 11).
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Figure 11a. Desmoplastic ameloblastoma in a 30-year-old woman. CT scan (a) and contrast-enhanced T1-weighted magnetic resonance (MR) image (b) demonstrate an expansile enhancing lesion within the right mandibular body (arrows) that causes significant buccal cortical destruction. (Fig 11 courtesy of Akifumi Fujita, MD, Jichi Medical University, Shimotsuke, Japan.)
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Figure 11b. Desmoplastic ameloblastoma in a 30-year-old woman. CT scan (a) and contrast-enhanced T1-weighted magnetic resonance (MR) image (b) demonstrate an expansile enhancing lesion within the right mandibular body (arrows) that causes significant buccal cortical destruction. (Fig 11 courtesy of Akifumi Fujita, MD, Jichi Medical University, Shimotsuke, Japan.)
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Odontogenic Myxoma.—
Odontogenic myxoma is clinically and radiographically indistinguishable from ameloblastoma, appearing as a multiloculated radiolucent lesion with internal osseous trabeculae. This rare tumor typically manifests in the second or third decade of life (8).
Calcifying Epithelial Odontogenic Tumor.—
Calcifying epithelial odontogenic tumor (Pindborg tumor) is composed of epithelial cells in a fibrous stroma. The tumor typically appears radiolucent with scattered calcified components. Most tumors are located in the premolar or molar region of the mandible and are associated with the crown of an impacted tooth (2).
Cementoblastoma.—
Cementoblastoma is a true (albeit rare) neoplasm of cementum that typically occurs in patients under 25 years of age. Usually found in association with the apex of the first molars, the lesion appears as a round, well-demarcated opaque sunburst mass with a thin radiolucent rim. Unlike with condensing osteitis, the periodontal ligament space becomes obscured by the lesion (2,9).
Ameloblastic Fibroma.—
Composed of epithelium representing enamel and embryonic connective tissue, ameloblastic fibroma typically appears as a well-defined, pericoronal radiolucent lesion. Most are multiloculated and associated with impacted teeth, often within the posterior mandible. Although ameloblastic fibromas do not represent a variant of ameloblastomas, they can appear radiologically as unilocular ameloblastoma (Fig 12) (10).
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Figure 12. Ameloblastic fibroma in a 15-year-old boy. Coronal reformatted CT image reveals a slightly lobulated, well-defined expansile lesion (arrows) within the right mandibular body. Note the prominent internal calcifications.
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Adenomatoid Odontogenic Tumor.—
Adenomatoid odontogenic tumor is a rare tumor that is typically diagnosed in the second decade of life, with the majority found in girls and young women. In addition, approximately 70% are found in the maxilla. The tumors appear as well-demarcated radiolucent lesions with varying amounts of punctate calcifications and can displace or prevent the eruption of teeth. If attached to a tooth, the lesions are found more apically on the root than are dentigerous cysts (Fig 13) (11). The characteristic imaging findings, along with appropriate patient demographic information, can help narrow the differential diagnosis.
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Figure 13. Adenomatoid odontogenic tumor in a 14-year-old boy. CT scan demonstrates a unilocular radiolucent lesion with a linear calcification (arrow) centered between the lateral incisor tooth and canine tooth. Note that the impacted tooth (arrowhead) is unaffected, a finding that indicates that the tumor developed after completion of odontogenesis.
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Primary Nonodontogenic Tumors
Ossifying Fibroma.—
Ossifying fibroma, also known as cemento-ossifying or cementifying fibroma, contains fibrous tissue with varying amounts of bony trabeculae. Typically diagnosed during the third and fourth decades of life, the majority of these tumors occur within the posterior mandible. The encapsulated, well-circumscribed lesion can appear radiolucent, radiopaque, or with mixed opacity depending on the degree of calcification. With maturation, the lesion becomes more radiopaque. Although the lesion is similar in appearance to fibrous dysplasia, its radiolucent boundary allows some distinction (Fig 14) (2,6).
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Figure 14. Ossifying fibroma in a 33-year-old woman. CT scan reveals a circular, partially calcified lesion (arrow) within the mandible. Note the internal ground-glass calcifications.
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Juvenile ossifying fibroma is an aggressively growing, destructive variant of the tumor, typically occurring in boys under 15 years of age. The lesion has been reported to arise within both the mandible and paranasal sinus regions, exhibiting rapid growth (3,12).
Periapical Cemental Dysplasia.—
Periapical cemental dysplasia forms from proliferation of connective tissue found within the periodontal membrane. The majority of lesions occur in women during the fourth and fifth decades of life. Most lesions are multifocal and occur between the mandibular canine teeth. They begin as a well-circumscribed radiolucent lesion at the apex of the tooth (Fig 15) and progressively change into a radiopaque mass surrounded by a radiolucent border. Simple bone cysts may develop within these lesions. Florid cemental dysplasia (florid cemento-osseous dysplasia) is the diffuse form of periapical cemental dysplasia and involves the entire mandible (3).
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Figure 15. Periapical cemental dysplasia in a 48-year-old woman. Occlusal radiographs demonstrate a well-defined radiopaque lesion (arrows) at the apex of a tooth. The advanced degree of calcification indicates maturity of the lesion.
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Solid Malignant Lesions
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Primary Odontogenic Tumors
The majority of carcinomas of the mandible are secondary to invasion from the surrounding mucosa (Table 6). Primary carcinomas include odontogenic carcinoma, primary intraosseous carcinoma, and malignant ameloblastoma. Some cases of carcinomatous transformation of OKCs have also been reported (3).
Odontogenic Carcinoma.—
Odontogenic carcinoma is a rare, aggressive intraosseous lesion consisting of poorly differentiated epithelial and clear cells. The lesion appears as a diffuse, "honeycomb"-like radiolucent lesion with surrounding cortical destruction. Because of the high rate of recurrence, prognosis is poor for patients with this tumor (2).
Ameloblastic Carcinoma–Malignant Ameloblastoma.—
Ameloblastomas of the mandible rarely become malignant; however, the potential for malignant transformation does exist. Although there is some controversy regarding terminology, most authors advocate the term ameloblastic carcinoma for tumors with typical cytologic findings of malignancy with or without metastasis. The term malignant ameloblastoma should be restricted to an ameloblastoma that is histologically benign but demonstrates evidence of metastasis. It is very difficult to distinguish these tumors from benign ameloblastomas at imaging alone, and histopathologic analysis is required for definitive diagnosis. However, aggressive features such as cortical destruction, extraosseous extension, and extensive solid components may suggest malignant potential (Fig 16) (13,14).
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Figure 16a. Ameloblastic carcinoma in a 17-year-old boy. (a) Contrast-enhanced CT scan (bone windowing) shows a multiloculated, enhancing soft-tissue mass (arrows) with adjacent bone destruction. (b) Axial contrast-enhanced T1-weighted MR image demonstrates the enhancing soft-tissue mass (arrows). (c) High-power photomicrograph (H-E stain) reveals innumerable ameloblastic cells with reversed polarity and nuclear pleomorphism (arrows).
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Figure 16b. Ameloblastic carcinoma in a 17-year-old boy. (a) Contrast-enhanced CT scan (bone windowing) shows a multiloculated, enhancing soft-tissue mass (arrows) with adjacent bone destruction. (b) Axial contrast-enhanced T1-weighted MR image demonstrates the enhancing soft-tissue mass (arrows). (c) High-power photomicrograph (H-E stain) reveals innumerable ameloblastic cells with reversed polarity and nuclear pleomorphism (arrows).
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Figure 16c. Ameloblastic carcinoma in a 17-year-old boy. (a) Contrast-enhanced CT scan (bone windowing) shows a multiloculated, enhancing soft-tissue mass (arrows) with adjacent bone destruction. (b) Axial contrast-enhanced T1-weighted MR image demonstrates the enhancing soft-tissue mass (arrows). (c) High-power photomicrograph (H-E stain) reveals innumerable ameloblastic cells with reversed polarity and nuclear pleomorphism (arrows).
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Primary Nonodontogenic Tumors
Various nonodontogenic solid malignant tumors occur in the mandible, but the mandible is not typically the primary site of diagnosis. Sarcomas such as osteosarcoma (Fig 17), chondrosarcoma, fibrosarcoma, and leiomyosarcoma can cause both osteolytic and osteoblastic lesions. A symmetrically widened periodontal membrane in a single tooth may be the earliest radiologic indication of osteogenic sarcoma of the mandible. Although mucoepidermoid carcinoma is typically associated with minor salivary glands of the buccal mucosa, a primary mandibular form occasionally occurs (Fig 18). Lymphoma and leukemia also have no pathognomonic findings and typically manifest as ill-defined osteolytic lesions of varying size. Multiple myeloma may also occur in the mandible, with or without the typical "punched-out" lesions. The ovoid radiolucent lesions will demonstrate no evidence of expansion or adjacent bone reaction but may erode the mandibular cortex (3). Patients with multiple myeloma may present with "chin numbness" due to involvement of the inferior alveolar nerve (Fig 19) (15).
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Figure 17a. Osteosarcoma in a 41-year-old man. (a) CT scan reveals osteoblastic changes (arrows) within the right mandibular body. Note the abnormal soft-tissue ossification (arrowhead). (b) Contrast-enhanced T1-weighted MR image demonstrates an ill-defined lesion (arrow) arising from periosteum. Note the decreased marrow signal intensity (arrowhead) involving the entire right mandibular body.
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Figure 17b. Osteosarcoma in a 41-year-old man. (a) CT scan reveals osteoblastic changes (arrows) within the right mandibular body. Note the abnormal soft-tissue ossification (arrowhead). (b) Contrast-enhanced T1-weighted MR image demonstrates an ill-defined lesion (arrow) arising from periosteum. Note the decreased marrow signal intensity (arrowhead) involving the entire right mandibular body.
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Figure 18a. Mucoepidermoid carcinoma in a 66-year-old man. CT scan (soft-tissue windowing) (a) and sagittal reformatted CT image (bone windowing) (b) show a large soft-tissue mass (arrows) that has destroyed the posterior body of the left mandible and extends into the buccal space. Note the invasion of the mandibular canal (arrowhead).
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Figure 18b. Mucoepidermoid carcinoma in a 66-year-old man. CT scan (soft-tissue windowing) (a) and sagittal reformatted CT image (bone windowing) (b) show a large soft-tissue mass (arrows) that has destroyed the posterior body of the left mandible and extends into the buccal space. Note the invasion of the mandibular canal (arrowhead).
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Figure 19a. Multiple myeloma in a 67-year-old man. (a) Panoramic reformatted CT image demonstrates sclerotic (arrow) and lytic (arrowhead) lesions in the mandible. (b) Axial T1-weighted MR image shows loss of the marrow fat within the right mandibular angle (arrow) and mandibular foramen (arrowheads).
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Figure 19b. Multiple myeloma in a 67-year-old man. (a) Panoramic reformatted CT image demonstrates sclerotic (arrow) and lytic (arrowhead) lesions in the mandible. (b) Axial T1-weighted MR image shows loss of the marrow fat within the right mandibular angle (arrow) and mandibular foramen (arrowheads).
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Metastasis.—
Metastatic disease often involves the mandible. Although the lesions are typically radiolucent with ill-defined borders, some blastic lesions such as prostate metastasis may occur. The most common sites of origin include the kidneys, lungs, and breasts; however, other primary sites have also been documented (Fig 20). Because of the increased marrow vascularity, the posterior body and angle are most commonly affected (16). Metastasis to the mandible is four times more common than metastasis to the maxilla. Identification of these lesions with accurate identification of the primary site is crucial, since approximately 30% of jaw metastases originate from an occult primary lesion (2).
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Other Lesions
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Infectious Lesions
Apical periodontitis.—
Apical periodontitis encompasses the spectrum of periapical cysts, granulomas, and abscesses. Most of these lesions are caused by dental caries and result in irreversible pulpitis. As mentioned earlier, apical cyst and granuloma are difficult to distinguish from each other at imaging. A thickened periodontal ligament space is the earliest sign for identifying these lesions in their cystic form. If the lesion progresses to an apical abscess, contrast-enhanced imaging will reveal an enhancing rim (Fig 21) (2).
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Figure 21a. Periapical and perimandibular abscess in a 10-year-old boy. (a) Contrast-enhanced CT scan demonstrates a rim-enhancing fluid collection (arrows) within the perimandibular soft tissues. (b) Oblique coronal reformatted CT image reveals a periapical abscess (thick arrow) within the mandibular body and a fistula (arrowhead) that extends to the lingual surface. Note the cavity (thin arrow) within the crown of the tooth.
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Figure 21b. Periapical and perimandibular abscess in a 10-year-old boy. (a) Contrast-enhanced CT scan demonstrates a rim-enhancing fluid collection (arrows) within the perimandibular soft tissues. (b) Oblique coronal reformatted CT image reveals a periapical abscess (thick arrow) within the mandibular body and a fistula (arrowhead) that extends to the lingual surface. Note the cavity (thin arrow) within the crown of the tooth.
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Osteomyelitis.—
Osteomyelitis, or infection of both the bone and marrow of the mandible, is rare in healthy individuals due to early administration of antibiotics (2). Its radiographic appearance ranges from acute or chronic suppurative to sclerosing osteomyelitis. Acute suppurative osteomyelitis (Fig 22) usually demonstrates no imaging findings in the early stages, whereas chronic lesions (Fig 23) demonstrate a variety of bone reactions, including radiolucent and radiopaque areas. Low-grade infections can cause sclerosing osteomyelitis, in which bone is deposited along the osseous cortex and trabeculae (17). Both focal and diffuse types have been described (Fig 24) (18,19).
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Figure 22a. Acute suppurative osteomyelitis in a 44-year-old woman. (a) CT scan (bone windowing) demonstrates a nonexpansile, osteolytic lesion (arrow) within the right mandible. Perimandibular soft-tissue inflammatory change (arrowheads) is also present. (b) High-power photomicrograph (H-E stain) reveals loss of osteocytes from lacunae and severe inflammatory cell infiltrates (arrows).
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Figure 22b. Acute suppurative osteomyelitis in a 44-year-old woman. (a) CT scan (bone windowing) demonstrates a nonexpansile, osteolytic lesion (arrow) within the right mandible. Perimandibular soft-tissue inflammatory change (arrowheads) is also present. (b) High-power photomicrograph (H-E stain) reveals loss of osteocytes from lacunae and severe inflammatory cell infiltrates (arrows).
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Figure 24. Sclerosing osteomyelitis in a 10-year-old boy. CT scan shows diffuse sclerotic changes with expansion of the left mandibular body (arrows). Note the diffuse soft-tissue swelling (arrowheads).
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Vascular and Neurogenic Lesions
Central Giant Cell Granuloma (Giant Cell Reparative Cyst).—
Central giant cell granuloma is believed to be a single lesion in a spectrum of altered vascular and reactive responses within bone (2). The lesion most frequently occurs in girls and young women during the second and third decades of life. The majority of these lesions are found in the anterior mandible. Initially, a giant cell reparative cyst manifests as a small, unilocular radiolucent lesion that can mimic an odontogenic cyst. With development, however, the lesion becomes multilocular, exhibiting a honeycomb appearance. Tiny bone septa are present traversing the lesion. There may be evidence of expansion, root resorption, and erosion or remodeling of the cortex. In addition, the lesion may cross the midline of the mandible. The differential diagnosis includes brown tumors of hyperparathyroidism, which can appear radiologically and histologically identical to giant cell reparative cysts. However, the patient’s age and laboratory test results should easily help distinguish between these two entities (Fig 25) (3–5).
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Figure 25a. Central giant cell granuloma in a 34-year-old man. (a) CT scan (bone windowing) demonstrates a cystic lesion (arrows) within the mandible. Note the erosion of the mandibular cortex. (b) Photograph of the gross resected specimen shows multiple cystic cavities (arrows). Photomicrography with H-E stain revealed multinucleated giant cells within the lesion.
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Figure 25b. Central giant cell granuloma in a 34-year-old man. (a) CT scan (bone windowing) demonstrates a cystic lesion (arrows) within the mandible. Note the erosion of the mandibular cortex. (b) Photograph of the gross resected specimen shows multiple cystic cavities (arrows). Photomicrography with H-E stain revealed multinucleated giant cells within the lesion.
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Arteriovenous Malformations.—
AVMs are abnormal, direct communications between arteries and veins. Although AVMs are uncommon in the jaw, they may occur within the ramus and posterior mandibular body (Fig 26). Identification of an AVM is important owing to the potential for fatal hemorrhage after tooth extraction. At radiography, the multiloculated lesions are cystic in appearance secondary to adjacent bone resorption. Angiography may be necessary to help confirm the diagnosis and for treatment planning (2,20).
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Figure 26a. AVM in a 28-year-old man. (a) Contrast-enhanced CT scan reveals multiple dilated and tortuous vessels (arrow) within the right masseter muscle. Note the abnormal enhancement (arrowhead) within the marrow of the mandible. (b) Axial T1-weighted MR image demonstrates a slightly expansile lesion (arrow) within the right mandibular angle and body. Multiple flow voids are present within the right masseter muscle. Note the loss of normal fatty marrow (arrowhead) within the mandible.
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Figure 26b. AVM in a 28-year-old man. (a) Contrast-enhanced CT scan reveals multiple dilated and tortuous vessels (arrow) within the right masseter muscle. Note the abnormal enhancement (arrowhead) within the marrow of the mandible. (b) Axial T1-weighted MR image demonstrates a slightly expansile lesion (arrow) within the right mandibular angle and body. Multiple flow voids are present within the right masseter muscle. Note the loss of normal fatty marrow (arrowhead) within the mandible.
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Central Hemangioma, Neurofibroma, and Schwannoma.—
Central hemangioma, neurofibroma, and schwannoma are usually well-defined soft-tissue structures with well-corticated margins. However, a central hemangioma may also manifest as a multilocular radiolucent lesion. There is often displacement of adjacent structures with root resorption. Widening of the inferior alveolar canal may be the only finding to indicate a neurofibroma (20–22).
Metabolic Abnormalities
Metabolic abnormalities may cause lesions in the mandible that appear similar to lesions occurring elsewhere in the body. Such systemic disorders include osteoporosis, osteomalacia, renal osteodystrophy (Fig 27), and osteitis fibrosa cystica (hyperparathyroidism) (2). Although some metabolic abnormalities appear similar to primary lesions such as fibrous dysplasia or Paget disease, the patient’s history alone usually allows the correct diagnosis to be made.
Tumorlike Lesions
Congenital lesions, developmental anomalies, and other tumorlike conditions such as condylar hypoplasia and torus mandibularis may occur in the mandible (Fig 28). Gardner syndrome (colo-rectal polyposis, soft-tissue tumors, and skeletal abnormalities) is a hereditary condition that manifests with multiple osteomas, also arising within the mandible (Fig 29). These well-defined radiopaque lesions are often associated with multiple impacted and supernumerary teeth (2). Epulis fissuratum is a diagnosis that is well known to dentists but often unfamiliar to general radiologists. The lesion consists of mucosal hyperplasia resulting from chronic low-grade trauma induced by a denture flange (Fig 30). Congenital epulis, a rare tumor seen in neonates, differs from epulis fissuratum in that it manifests as pedunculated, alveolar mucosal lesions (23). Fibrous dysplasia (Fig 31) and osteitis deformans (Paget disease) appear the same in the mandible as they do in other parts of the body.
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Abstract
LEARNING OBJECTIVES FOR TEST...
