Orthognathic surgery with removal of lipoma in the asymmetric mandibular prognathism of a patient with a mandibular bone defect due to intramuscular lipoma on the medial aspect of the ramus: a case report.

Lipomas, the most common soft-tissue mesenchymal neoplasms in adults, are characterized by the proliferation of mature white adipocytes without cytologic atypia. Lipomas are rarely observed in the head and neck region. We present a case of resection and orthognathic surgical removal of an intramuscular lipoma of the mandible with involvement of the mandibular ramus and condylar head and neck. An 18-year-old female patient was referred to our hospital for orthognathic surgery for the management of facial asymmetry and mandibular prognathism. The patient did not present with facial swelling, pain, or temporomandibular dysfunction; however, on radiographic examination, including cone-beam computed tomography and magnetic resonance imaging, an infiltrative fatty lesion was observed in the masticator space inside the right mandible, and the adjacent mandible exhibited bone thinning and deformity. Resection of the lipoma was performed along with orthognathic surgery, including a Le Fort I osteotomy for the maxilla and bilateral sagittal split ramus osteotomy (BSSRO). In this case, because the ramus was split using BSSRO, accessing the lipoma intraorally was easy. Consequently, aesthetic scarring was avoided, and no complications, such as unfavorable splitting or pathologic fracture, occurred. Although recurrence has not been observed about 1 year, long-term follow-up should be performed.