Primary leiomyosarcoma localized in the mandibular bone is exceptional. We report a case with active intraosseous development and review eight other cases in the literature. The clinical signs at discovery were nonspecific. Radiological imaging showed osteolysis with no periosteal reaction. MRI was required to study extension to soft tissues and was useful for guiding wide excision. The risk is dominated by distant metastasis rather than locoregional extension. The histological diagnosis is difficult and requires an immunohistochemistry study. No therapeutic consensus has been established.