Multiple osteomas are associated with Gardner's syndrome. The etiology of osteomas is unclear. They may be related to osteoblastomas or may simply be a developmental anomaly. The fact they are often found in the auditory canals of swimmers and divers who frequent cold water suggests that they are some type of inflammatory reaction. The radiological appearance of osteomas depends on their location.
Central osteomas are well delineated sclerotic lesions with smooth borders.
Peripheral osteomas are radiopaque lesions with expansive borders that may be sessile or pedunculated. There are two types of osteomas microscopically. They have no Haversian canals and no fibrous component. Trabecular osteomas are composed of cancellous trabecular bone with marrow surrounded by a cortical bone margin. Treatment of osteomas is only necessary if they are symptomatic.