Incidental Finding on a Panoramic Radiograph
A 58-year-old woman presents for a routine dental examination. She is asymptomatic. A panoramic radiograph reveals a well-defined, unilocular radiolucency in the right posterior mandible, located at the angle, measuring approximately 2.5 cm in diameter. The lesion is associated with the crown of an impacted third molar, which is displaced superiorly and posteriorly. The root of the adjacent second molar appears to be displaced mesially. There is no cortical expansion, no root resorption, and no associated soft tissue swelling. The patient's medical history is unremarkable. You are considering the differential diagnosis and the next steps in management.
1. What is the most likely diagnosis, and what are the key radiographic features that support it?
Read the worked answer
The most likely diagnosis is a dentigerous cyst. Key features: well-defined, unilocular radiolucency attached to the CEJ of an impacted tooth, enclosing the crown. The lesion is associated with an impacted third molar, which is a common site. The displacement of the tooth and adjacent root suggests a slow-growing, expansile lesion. Other possibilities include an odontogenic keratocyst (OKC), which can also be associated with an impacted tooth but often shows more aggressive behavior and a higher recurrence rate; an ameloblastoma (unicystic), which can mimic a dentigerous cyst but often shows more cortical expansion and root resorption; and a unicystic ameloblastoma. However, the lack of cortical expansion and root resorption favors a dentigerous cyst. The definitive diagnosis requires histopathologic examination after biopsy or excision.
2. What is the appropriate management plan, and what factors would influence your decision?
Read the worked answer
Management options include: enucleation of the cyst with removal of the impacted tooth, marsupialization (decompression) followed by enucleation, or observation if the lesion is small and asymptomatic. Factors influencing the decision: patient's age (58 years), size of the lesion (2.5 cm), proximity to the inferior alveolar nerve, and the potential for recurrence. Given the size and the impacted tooth, enucleation with removal of the tooth is often performed. However, if the cyst is large and close to the nerve, marsupialization may be considered to shrink the cyst before enucleation. The specimen should be sent for histopathologic examination to confirm the diagnosis and rule out OKC or ameloblastoma. Postoperative follow-up with radiographs is necessary to monitor healing and recurrence.