Adenomatoid odontogenic tumour (AOT) is a benign tumour of odontogenic origin. The differential diagnosis of AOT is crucial in terms of surgical management. The 23-year old male patient presented in this case study was referred to the maxillofacial surgery clinic due to the incidental radiological finding of a large osteolytic lesion of the anterior mandible with a retained permanent canine at the base of the bone. Ultrasound imaging revealed the anterior surface of the tooth inside the lesion, indicating extreme thinning of the maintained cortical bone and liquid filling of the cystic lesion. Surgery revealed a bone defect with a deformed, incomplete tooth inside a granulation-like soft tissue. The tooth was extracted and the soft tissues were excavated. Healing was uneventful. Radiographic and physical investigations during long-term follow-up demonstrated complete bone remodeling. Some areas of the tumour were alpha-smooth-muscle-actin positive, indicating a myoepithelial differentiation. Differential diagnosis of AOT to other odontogenic tumours, such as ameloblastoma, is crucial for therapy. Exact morphological diagnosis avoids extensive ablative surgery.
