Peripheral osteoma in an unusual region of the mandible: A case report


Osteomas are benign tumors characterized by bony growth that commonly occur in the sinuses. Peripheral osteomas in the jawbone are relatively uncommon, with only 8 cases, including the present case, reported in the mandibular sigmoid notch. The patient had a peripheral osteoma that developed from the sigmoid notch of the mandible to the condylar neck. We performed panoramic radiography and computed tomography (CT) for preoperative image analysis, and created a three-dimensional model based on the CT data. Using the model, we were able to explain the lesion to the patient in an easy-to-understand manner. The pathological diagnosis of the resected specimen was peripheral osteoma. At 21 months after the operation, no recurrence has been observed.


  • Peripheral osteoma are benign tumors that mainly occur in the sinuses.

  • Surgical resection is commonly used as treatment.

  • It is extremely rare to occur around the sigmoid notch of the mandible, and so far only 7 cases have been reported.

  • We experienced a peripheral osteoma that developed around the sigmoid notch of the mandible.


Osteomas are benign tumors composed of mature compact or cancellous bone and are characterized by painless slow growth. Osteomas are classified as central, peripheral, or extraskeletal types [ ]. Central osteomas arise from the endosteum, peripheral osteomas from the periosteum, and extraskeletal soft-tissue osteomas from within a muscle [ ]. Clinically, peripheral osteoma appears as a unilateral, sessile or pedicled, well-circumscribed, mushroom-like mass ranging from 10 to 40 mm in diameter [ ], and can arise at any age with no sex predilection [ ]. Although the exact etiology and pathogenesis of peripheral osteomas remain unclear [ ], there are various reports on their possible origins, including trauma, inflammation, infection, and muscle traction [ , , ]. Peripheral osteomas mainly occur in the sinuses, and are rarely found in the jawbone [ ].

Although several papers have described peripheral osteomas of the jawbone [ ], only 7 cases of peripheral osteomas in the sigmoid notch of the mandible have been reported. The incidence of the sigmoid notch of the mandible peripheral osteoma is only 1.6% among mandibular peripheral osteomas [ ].

We report a 69-year-old woman with peripheral osteoma in the sigmoid notch of the mandible. In addition to the imaging diagnosis, a three-dimensional (3D) model was created, which was effective for providing an explanation to the patient.

Case report

A 69-year-old female presented to our department with the chief complaint of swelling on the left side of the anterior part of the tragus. She had been aware of the swelling for 2.5 years, but had not taken any action because she had no pain. An interview confirmed that the patient had no medical history of trauma or temporomandibular disorders.

An extraoral examination revealed mild facial asymmetry, but no trismus or occlusal deviation was observed. The patient had no functional problems. A mass was detected in the left side of the preauricular region.

On a panoramic radiograph, an oval radiodense mass was detected at the sigmoid notch of the left mandible ( Fig. 1 A). Three-dimensional computed tomography (CT) showed a bony lesion arising from the left mandibular neck with dimensions of 25 × 20 × 15 mm ( Fig. 1 B). Using the CT data and Zedview software (LEXI Inc., Tokyo, Japan), we created a 3D model of the mandible ( Fig. 2 ) to facilitate an explanation to the patient.

Fig. 1
Preoperative examination. A: Panoramic radiograph showing an oval radiodense mass at the left sigmoid notch of the mandible. B: Preoperative three-dimensional computed tomography image revealing a bony lesion in the left sigmoid notch of the mandible.

Fig. 2
Three-dimensional model of the mandible.

A clinical diagnosis of peripheral osteoma in the left mandibular neck was made. On January 22, 2019, we performed surgery under general anesthesia ( Fig. 3 ). A bone-like mass that was milk-white, smooth, slightly uneven, and pedunculated was removed using a bone chisel and a dental round bur, taking care not to create a mandibular neck fracture. The mass was completely removed.

Fig. 3
Intraoperative view of the lesion exposed by the high perimandibular approach.

Histopathological examination of the surgically resected hard-tissue mass revealed irregular growth of mature lamellar bone to form thick trabecular bone, and cortical bone covering the surface layer ( Fig. 4 ). A mosaic image reflecting modeling was clearly confirmed in the remodeled bone. The intertrabecular spaces were composed of sparse fibrous tissue, and osteoblasts were seen on the surface of the trabecular bone.

Fig. 4
Examination of the resected specimen showed that lamellar bone had grown irregularly to form thick trabeculae, and that the surface layer was covered with cortical bone.

Based on the preoperative examination, radiological, and histological findings, we established a diagnosis of peripheral osteoma. After the operation, we performed panoramic photography and 3D-CT imaging to confirm that the osteoma had been removed ( Fig. 5 ). No recurrence or dysfunction has been observed for 21 months after the operation.

Mar 21, 2021 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Peripheral osteoma in an unusual region of the mandible: A case report
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