157 Osteoblastoma is an uncommon, benign bone neoplasm
that is rare in the jaws. The neoplasm characterized by hypocellular mineralized tissue that may form large masses or irregular trabeculae. This tumor occurs most often in the spine of a young person. Although osteoblastoma can involve any bone of the skeleton, the long tubular bones are the most commonly affected (26 to 36% of cases) followed by the spinal column (21 to 33% of cases). In approximately 10% of cases, this tumour has been found in the maxillofacial skeleton with a greater frequency occurring in the mandible [1-3]. Osteoblastoma should be differentiated from osteoid osteoma, cementoblastoma, cemento-ossifying fibroma, or osteosarcorma.
Osteoma is a benign osteogenic neoplasm characterized by proliferation of compact or cancellous bone. It is usually in an endosteal location (endosteal or central osteoma), periosteal location (periosteal or peripheral osteoma) and uncommonly
within soft tissue (extraskeletal osteoma) [4]. The growth of the tumour is origind by the activity of either the periosteum or the endosteum. Peripheral osteomas are regarded as centrifugal growth from the periosteum, while central osteomas arise centripetally from the endosteum [5]. Osteoma should be differentiated from idiopathic osteosclerosis, sclerosing osteitis, buccal and lingual exostoses, or mandibular tori.
We reported a case of osteoblastoma occurring in coronoid process of the mandible mimicking osteoma, and described radiographic features of osteoblastoma and osteoma in the maxillofacial region.
Case Report
A 20-year-old woman was presented with complaint of protruding mass in yawning or tooth-brushing, affected the left side of her mandible. She had noticed the mass for the last one year, but it was not changing in size.
On intraoral inspection, there was a hard palpable mass with normal mucosal surface lingual to the left masseter area.
Intraorally a hard mass was palpable on the left cheek during mouth opening. Clinical examination revealed no facial asymmetry, swelling, or deviation on mouth-opening. She had no facial trauma or significant medical history. All laboratory ORAL BIOLOGY RESEARCH 2013; 37(2): 157-160
Periosteal osteoblastoma of the mandible mimicking an osteoma: Case report
Yo-Seob Seo, Jae-Duk Kim, Jin-Soo Kim*
Department of Oral and Maxillofacial Radiology, School of Dentistry, Chosun University, Gwangju, Korea
ABSTRACT
Osteoblastomas are uncommon tumors that account for approximately 1% of all primary bone tumors. This report presents the cone-beam computed tomography (CBCT) findings of an osteoblastoma of the coronoid process of the mandible. Initially, this lesion was judged as an osteoma. CBCT images revealed a large mass with multiple internal calcifications. Histopathological examination of the lesion confirmed it as an osteoblastoma.
Key Words: Osteoblastoma, Osteoma, Cone-beam computed tomography Case Report
Received Aug 23, 2013; Revised version received Sep 5, 2013 Accepted Sep 7, 2013
Corresponding author: Jin-Soo Kim
Department of Oral and Maxillofacial Radiology, School of Dentistry, Chosun University, 309 Pilmun-daero, Dong-gu, Gwangju 501-759, Korea
Tel: 82-62-220-3884, Fax: 82-62-227-0270 E-mail: [email protected]
This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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values were within normal limits.
Panoramic radiograph revealed a well circumscribed radiopaque mass superimposed with the left maxillary third molar and the left coronoid process of the mandible (Fig. 1).
Cone-beam computed tomography (CBCT) was performed to obtain a definitive diagnosis. A coronal and sagittal CBCT scan showed a well-circumscribed radiopaque mass attached to the affected bone. The coronal CBCT scan showed a bone- like, well-circumscribed, radiopaque mass outer side of the left maxilla (Fig. 2). The axial CBCT scan showed mixed radiolucent and radiopaque mass attached to the mandible (Fig. 3). In addition, reconstruction images were obtained to evaluate its 3-dimensions (3D) and relation to the surrounding structures (Fig. 4). In the 3D reconstruction, a bone-like mass was clearly observed on the front of the left ramus just below the coronoid process (Fig. 4C).
A tentative diagnosis was periosteal osteoma. Under general anesthesia, the mass was excised and submitted for histopathologic evaluation.
On histopathological examination, the submitted specimen disclosed anastomosing irregular trabeculae with osteoblastic rimming. Pathologic diagnosis was osteoblastoma by the presence of osteoblatic rimming.
Discussion
Osteoblastoma is an uncommon, benign bone-forming neoplasm with potential for aggressive growth, characterized by osteoblastic rimming of woven bony trabeculae. It represents 1% of tumors affecting the skeleton and only 10% of these tumors are found on the face [3,6,7]. Osteoblastoma are found both in the tooth-bearing regions and commonly around the
Fig. 1. Preoperative panoramic radiograph of the patient showing the radiopaque mass superimposed with the left maxillary third molar and the left coronoid process of the mandible.
Fig. 2. Coronal cone-beam computed tomography scans showing a bone-like, well-circumscribed, radiopaque mass outer side of the left maxilla.
Fig. 3. Axial cone-beam computed to- mography scan showing mixed radio- lucent and radiopaque mass attached to the mandible.
Yo-Seob Seo et al.
159 temporomandibular joint (within the condyle or the temporal
bone). Ahmed and Nwoku [7] showed only 3 cases appeared in the temporomandibular joint area and another 3 cases involved the coronoid process of the mandible. In our case, the tumor was located in the coronoid region of the mandible, and was well demarcated radiographically.
Osteoblastoma, which accounts for less than 1% of all tumours of bone, commonly occurs in children and young adults, with a peak incidence in the first three decades of life.
The tumour has a definite predilection for males. Clinically, patients often report pain and swelling of the affected region [3,6,8]. In the review by Gordon et al. [3] there was pain in 75% of the cases. It may occur close to the root of a tooth and sometimes causes tooth mobility or displacement.
Osteoblastomas often display a benign tumor radiographic aspect. However, their radiographic appearance is generally nonconclusive and may mimic other conditions, benign and malignant [8].
Radiographically osteoblastoma may appear as a radiolucent lesion that can be ill- or well-defined, depended on the radiologic diagnostic technique available at the time of diagnosis [3]. The radiograph manifestations were a round or elliptical, substantive, well-defined lesion with a cortical border [9]. Bone expansion and patchy or cloudy calcification was seen in unicystic and multicystic radiolucencies. Mature lesions were characterized by central, high-density radiopacities with a radiolucent rim. The radiographs of aggressive osteoblastoma, while demonstrating an expansile mass, reveal a radiolucent rim surrounding the lesion [10]. Periosteal osteoblastoma presents as a round or ovoid
heterogeneous mass attached to the cortex, grows rapidly and is painful [11].
The radiographic appearance of benign osteoblastoma is not diagnostic. Furthermore, the tumor of the jaw bone is not clinically distinctive. Therefore, fibro-osseous lesions and tumors of bony origin should be considered in the differential diagnosis [7]. Jones et al. [12] reviewed 77 cases of osteoblastoma of the jaws, including their 24 cases. Twenty- one cases (27.3%) were described as radiolucent, 22 (28.6%) as radiopaque and 21 (17%) as combined radiolucent/radiopaque lesions. Only one case arose as a periosteal lesion on the buccal cortex of the right posterior mandible. Two cases of the 24 cases were thought to represent an osteoma. Lin et al. [9] reviewed 82 cases of osteoblastomas occurring in the maxillofacial region in the recent decade, including their 2 cases. Twenty- seven cases (33.8%) were radiopaque masses; 20 were low- density, cystic radiolucencies with inner calcification (25%);
12 were mixed radiopaque and radiolucent lesion (15%). The border of osteoblastoma may be diffuse or may show some sign of a cortex. Lesions often have a soft tissue capsule around the periphery, indicating that this tumor is more mature in the central regions where there is evidence of abnormal bone.
Osteobalstomas can expand bone, but usually a thin outer cortex is maintained. This lesion may invaginate the maxillary sinus or the middle cranial fossa. Our case revealed radiopaque mass attached to cortical bone of the mandible with an internal mixed radiolucent and radiopaque density. Therefore, the first impression of the present case was osteoma, because the panoramic radiograph and CBCT scans showed the typical Fig. 4. Cone beam computed tomography reconstruction showing the bony mass attached to the mandible.
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features of peripheral osteoma such as bony expansion. We should be considered of periosteal osteoblastoma. However our case had no growing signs and symptoms.
Osteoma, a slow-growing benign osseous neoplasm, is characterized by a proliferation of osteoblasts that form bone trabeculae in the connective tissue stroma. This neoplasm is an uncommon condition that generally occurs in the maxillofacial bones. The neoplasm may be clinically silent for years without any symptoms [13,14]. It is usually diagnosed when it becomes enlarged and is incidentally observed during a radiological examination.
Traditional radiographic imaging is generally sufficient to diagnose an osteoma. It appears as a radiopaque mass with a density similar to normal bone. A panoramic radiograph, or a Waters’ view usually shows the position and benign nature of the lesion. CT scanning makes it possible to achieve a better resolution [15] and a more precise localization, especially with 3D reconstruction.
The radiographic characteristic of osteoma is classically a well circumscribed round or oval mushroom-like radiopaque mass with distinct borders [16,17]. The lesion attached to the cortical plates with a broad base. If a peripheral osteoma is pedunculated, a narrow contact area can be seen between the lesion and the compact bone. In our case, the lesion consisted of mixed radiolucent and radiopaque bone with narrow pedicle demonstrated by CBCT.
Periosteal osteoblastoma and osteoma, which perhaps should also be considered in a differential diagnosis, are more frequently painful and may exhibit a more rapid rate of growth than osteoma. The osteoblastoma shows a significant tendency to recur (13.6%) [3], which needs careful diagnosis, surgical management and follow-up.
Acknowledgments
This study was supported by research funds from Chosun University Dental Hospital, 2013.
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