Parotid salivary gland carcinoma in a geriatric horse

Abstract

This case report describes a geriatric gelding with a 2 month history of fast-growing masses within the parotid and submandibular regions. The horse was dyspnoeic on presentation and upper airway endoscopy revealed partial airway obstruction at the level of the pharynx, secondary to a space-occupying mass. Cytological evaluation of multiple fine-needle aspirates obtained from the masses were suggestive of salivary gland neoplasia, therefore the horse was subjected to humane euthanasia. A computed tomographical scan was obtained post mortem and revealed a large multi-lobulated mass involving both guttural pouches, resulting in 80% occlusion of the naso- and oropharynx. Histopathology confirmed a parotid salivary gland carcinoma (papillary-cystic type). Salivary gland tumours are extremely rare in horses, with only a few cases reported in the literature. Treatment of these malignancies proves to be challenging, requiring complete parotidectomy or surgical debulkment, in combination with adjunctive therapy.