Computed tomographic findings in 25 cats with ear canal neoplasia.

Computed tomography is commonly used to evaluate feline otic disease; however, published studies characterizing the CT appearance of ear canal neoplasia are limited. The purpose of this multicenter, retrospective, secondary analysis, cross-sectional study was to describe the CT features of histopathologically confirmed feline ear canal neoplasia. The CT studies of 25 cats with ear canal neoplasia were prospectively scored 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 mass, attenuation characteristics, features of contrast enhancement, involvement of otic structures, calvarial and brain changes, changes of nearby structures, and lymphadenopathy. There was a significant overlap of CT findings between cats with malignant ceruminous gland neoplasia, ceruminous gland adenoma, and squamous cell carcinoma (SCC). Ceruminous gland adenoma was typically homogeneous in attenuation with homogeneous contrast enhancement and no intralesional fluid accumulations (IFAs) or involvement of adjacent structures. In contrast, SCC consistently had heterogeneous attenuation, heterogeneous contrast enhancement, IFAs, and involvement/invasion of adjacent structures. Malignant ceruminous gland neoplasia had variable attenuation and pattern of contrast enhancement with occasional IFAs and occasional involvement/invasion of adjacent structures. Knowledge of these imaging features will inform the creation of prioritized differential diagnosis lists. However, a biopsy is required to confirm the diagnosis.