Osteochondroma of the coronoid process: A case report and review of the literature.

Osteochondroma (OC) is considered the most common tumor of the axial skeleton, although it is relatively uncommon in the craniofacial region. The present study describes an atypical case of OC of the coronoid process. A 34-year-old woman presented with severely limited mouth opening (5 mm) and swelling of the right zygoma. Cone-beam computed tomography (CBCT) revealed a mushroom-shaped outgrowth from the coronoid process to the inner surface of the zygomatic arch, forming a pseudojoint. The patient was treated with coronoidectomy via an intraoral approach. Histopathological examination revealed features suggestive of OC. Subsequently, the patient was able to open their mouth, and there was no evidence of recurrence or post-operative complications in the 21-month follow-up. A review of the literature revealed only 38 histologically proven cases of coronoid OC in the past 30 years (1989-2018). The incidence of the disease was higher in men compared with that in women (male:female, 2.17:1), and the median age at onset was 28.7 years, with a range of 5-57 years. Gradual limitation of mouth opening and facial asymmetry are the most noticeable symptoms. Water's view and submentovertex projection of the zygomatic arch may be useful in identifying the tumor and its association with the zygoma, while CT and CBCT permit a detailed visualization of the location and density of the tumor. Coronoidectomy is the preferred treatment option, and the prognosis is excellent, with no evidence of recurrence or malignant transformation.