Case Study

CT Neoplastic Mass Lesion within the External Auditory Canal in a 7 year old MN Cocker Spaniel Dog

The patient presented for a mass in the right ear canal which was tentatively diagnosed as a cutaneous plasma cell tumor by FNA at the RDVM. There is a history of ear infections, currently being treated with Baytril. There is also a history of a cutaneous plasma cell tumor that was removed from the oral cavity in April 2015.

Physical Exam: BAR with a body condition score of 6/9. Eyes, ears, nose and throat WNL. A moderate amount of dental calculus was noted on the teeth. Gingiva were pink, CRT 2 seconds. The coat was healthy. No cardiac murmur or arrhythmias auscultated. BVS WNL. Abdominal palpation soft, non-painful. Neurologic system WNL. The gait was ambulatory x 4. Musculoskeletal system appeared to be NSF. Pain Scale (Colorado 0-4) – 0-1.

Image Interpretation

CT of the head, plain series: The skull conformation is typical for a Cocker Spaniel, which includes relatively small and thick-walled tympanic bullae. Both external auditory canals are narrow in conformation. The horizontal part of both external auditory canals shows centripetal wall thickening bilaterally which is slightly more pronounced on the right side. There is a cauliflower shaped, soft tissue attenuating mass lesion within the right external auditory canal at the junction between its vertical and horizontal part. The mass lesion measures approximately 10 mm in diameter, the auditory canal lumen is occupied entirely, and there is mild expansion of the auditory canal. The remainder of the auditory canal lumen and tympanic bulla do not show any accumulation of inflammatory secretions at present.
The brain does not show abnormalities regarding shape or attenuation. The right medial retropharyngeal lymph nodes show very mild increase in size whilst the short-long axis ratio is preserved. The nasal septum is mildly oblique, the nasal conchae show mild hypoplasia and reduced folding.

DX

Neoplastic mass lesion within the right external auditory canal and mild reactive lymphadenopathy

Outcome

Differential diagnosis includes an inflammatory polyp next to various types of mesenchymal and epithelial soft tissue neoplasia. The computed tomography is not specific for a malignancy, but further assessment of the lesion character requires sampling and histopathological examination. As an alternative approach, the lesion may be removed entirely as a biopsy sample.
Full staging should further include chest radiographs and fine needle aspiration of the lymph nodes.