Computed Tomographic Features of Benign and Malignant External Ear Canal Neoplasms in 39 Dogs.

Computed tomography (CT) is commonly used to evaluate external and middle ear disease and for surgical planning in dogs. However, there is limited literature regarding CT characteristics of benign and malignant canine external ear canal neoplasms. This retrospective, multicenter, secondary analysis, cross-sectional study compared the CT features of benign and malignant tumors in 39 dogs with 41 external ear canal masses by consensus of two veterinary radiologists. Recorded parameters were the presence of focal or multifocal tissue enlargement (mass/masses), lesion shape, location of the center of the mass, attenuation characteristics, features of contrast enhancement, involvement of otic structures, calvarial and brain changes, changes of nearby structures, and lymphadenopathy. The most common neoplasms in this study were ceruminous gland adenocarcinoma (13/41) and ceruminous gland adenoma (11/41). Although malignant tumors more commonly exhibited heterogeneous attenuation, heterogeneous contrast enhancement, aggressive periosteal proliferation, and compressed/displaced and/or invaded regional structures, benign tumors also exhibited aggressive characteristics, such as adjacent osteolysis. Given the degree of overlap of CT findings between benign and malignant external ear canal neoplasms, features may only aid in prioritizing differential diagnoses, and biopsy is required for definitive diagnosis.