Fibro-osseous lesions of the external auditory canal

Abstract

Objectives: To differentiate a novel type of benign circumscribed bone lesion of the external auditory canal from those described previously, such as exostoses and osteomas. Study Design: Information was obtained from computed tomography (CT) images, surgical findings, and pathologic study. Methods: Five patients (26 to 82 years old) who presented a hard, round, unilateral, skin-covered mass occluding the external auditory canal to varying degrees were studied. ACT study carried out before resection of the lesions by curettage disclosed the absence of a bony connection to the underlying structures. All the tissue specimens underwent pathologic study. Results: CT and surgical findings demonstrated the absence of a connective pedicle. The pathologic findings showed lesions consisting of an osteoma- like bone formation with sparse osteoblastic areas; mature lamellar bone was observed in three cases, bone marrow containing adipose tissue and hematopoietic remnants in two, and a dense, collagenous stroma in another. They all showed irregular trabeculae, bordered by osteoid osteoblasts. In no case was there evidence of a relationship to the cartilaginous tissue or to the bony structures of the external auditory canal. Conclusions: The data obtained from the clinical, CT, surgical, and pathologic findings suggest the existence of a lesion unlike those previously known, possibly related to ossifying reactions in other parts of the organism.