A case of multiple osseous choristomas arising on the medial side of the lateral pterygoid muscle.

Osseous choristoma is a rare entity in the oral and maxillofacial region. The most common site is the tongue, followed by the buccal mucosa. Osseous choristoma of the muscle is unusual and few cases have been described in the literature. No reports have described osseous choristoma arising on the medial side of the lateral pterygoid muscle. Herein, we report the first such case. A 61-year-old woman was referred to our facility for treatment of temporomandibular joint disorder. Computed tomography (CT) revealed two osseous lesions on the medial side of the lateral pterygoid muscle. Preoperatively, a three-dimensional (3D) life-sized model of the skull was fabricated from the CT imaging data. The 3D skull model was used to clarify the 3D positional relationships of the osseous lesions relative to the surrounding anatomical structures. Surgery to remove the osseous lesions was performed under general anesthesia. Unfortunately, only the larger of the two masses was able to be resected because of the risk of nerve and vascular injury. Histological examination revealed that the resected lesion comprised mature lamellar bone with regular osteocytes and no atypia. The diagnosis was multiple osseous choristomas based on the histological and clinical findings.