Primary aneurysmal bone cyst of coronoid process

Abstract

Background: Aneurysmal bone cysts are relatively uncommon in the facial skeleton. These usually affect the mandible but origin from the coronoid process is even rarer. To the best of our knowledge, this is the first reported case of a coronoid process aneurysmal bone cyst presenting as temporal fossa swelling.

Case presentation: A 17 year old boy presented with a progressively increasing swelling in the left temporal region developed over the previous 8 months. An expansile lytic cystic lesion originating from the coronoid process of the left mandible and extending into the infratemporal and temporal fossa regions was found on CT scan. It was removed by a superior approach to the infratemporal fossa.

Conclusion: Aneurysmal bone cyst of the coronoid process can attain enormous dimensions until the temporal region is also involved. A superior approach to the infratemporal fossa is a reasonable approach for such cases, providing wide exposure and access to all parts of the lesion and ensuring better control and complete excision.

Figure 1

Axial and coronal sections of CT scan showing rounded expansile lesion of bone with cortical thinning, mostly occupied by hypodense fluid with scattered areas of hyperdensity with in it.

Figure 2

Peroperative photograph showing a thin walled cyst with brownish serous fluid coming out of it. (P = pinna, Z = arch of zygoma, C = aneurysmal bone cyst)

Figure 3

Microphotograph showing vascular spaces separated by septa containing giant cells and fibroblasts. (H&E 250×)