Species and history: Cat (European Shorthair), 11 years old, living prevalently outdoor. Bilateral ulcerated nodular masses of the external ear (pinna). The cat underwent surgery (bilateral conchectomy).
Organ: External ear (cartilaginous pinna).
Description: The apical part of the pinna (right ear) is affected by two distinct but adjacent tumors. The first one (on the right) has an infiltrative pattern and is composed of cords, islands, and papillae of epithelial cells with squamous differentiation originating from the epidermis and invading the dermis and auricular cartilage. The second one (on the left) has an expansive growth pattern and is characterized by the proliferation of spindle-shaped cells organized into small bundles and whorls. Numerous mitoses and moderate atypia are observed in both proliferations. Epidermis is extensively ulcerated.
Morphological diagnosis: Squamous cell carcinoma (SCC) and Soft tissue sarcoma (STS) of the pinna.
Comments: SCC is one of the most common cutaneous malignant tumor in cats with a predilection for poorly pigmented areas of the pinna. Chronic exposure to UV-radiation is the primary cause of this neoplasia.
STS of the pinna is a relatively rare tumor in cats. The most common malignant mesenchymal tumor in this site is fibrosarcoma.
The diagnosis of two malignant distinct tumors in the external ear in an extremely rare event.
Authorship: Giovanni Di Teodoro (DVM, PhD, MSc Vet Path), Istituto Zooprofilattico Sperimentale dell’Abruzzo e del Molise (IZS Teramo).
References: Tumors in Domestic Animals, ed. Donald J. Meuten, fifth edition, chapter 21: tumors of the Ear, pp. 923-941.