Osteosarcoma arising from the mandibular fossa of the temporal bone misdiagnosed as temporomandibular joint disorder: Case report

Primary head and neck osteosarcomas (HNOS) arising from skull base are rare. It may be difficult to detect in the early stage. We discuss the symptoms that should be noted in daily clinical practice. We aimed to present a case of an osteosarcoma (OS) arising from the mandibular fossa of the temporal bone that was initially misinterpreted as temporomandibular disorder (TMD). Since TMD is a common disease, other rare serious diseases can be misinterpreted as TMD at an early stage. Spontaneous pain, swelling, maximal diameter of mouth opening of less than 20 mm, long-term trismus, and neurological symptoms, may be useful in the differential diagnosis of TMD. If there is a possibility that it is not TMD, it may be better to employ other diagnostic modalities such as CT or MRI to investigate the possibility of HNOS.