Keratocystic odontogenic tumor arising at the mandibular ramus with an impacted tooth: a case report and mimic lesions

Objectives: To consider the biologic behaviors of keratocystic odontogenic tumors (KCOTs) and

ameloblastomas and dentigerous cysts.

Methods: A 63-year-old Japanese man presented with swelling and discomfort in the left cheek during jaw movement. Examination revealed a multilocular lesion within the mandible extending from the left second premolar to the left mandibular ramus and coronoid process; the lesion contained a deviated impacted tooth. The tumor had expanded beyond the bone and was invading the masseter and medial pterygoid muscles. Marginal mandibulectomy with a free iliac bone graft was performed.

Results: No recurrence was observed during a 7-year follow-up.

Discussion: The histopathological diagnosis of the lesion showed it was a KCOT. These tumors usually grow within the bone, causing bone expansion. However, this tumor had expanded beyond the bone and invaded surrounding muscles. Thus, KCOTs can, in rare cases, manifest themselves as described here. Evaluating preoperative images and histopathological findings is important to determine the optimal treatment strategy.