Adenosquamous carcinoma of the cervical oesophagus in a dog

ABSTRACT: A 9-year-old male Shih Tzu dog presented with a mass on the ventral region of the neck and developed ptyalism. Radiographs revealed a radiodense nodule located in the mid-third of the oesophagus compressing the trachea. Preoperative cytology showed large neoplastic cells with abundant vacuolated cytoplasm arranged in clusters. The nodule was removed by oesophagectomy and submitted for histopathology. Microscopically, the oesophageal mass was multilobulated and unencapsulated. It had a mixed cellular growth pattern with areas showing squamous and glandular differentiation. The squamous component of the tumor was formed by solid strands of neoplastic epithelial cells; many neoplastic cells had undergone central keratinization and sometimes formed keratin pearls. The deeper adenocarcinomatous portion of the tumor consisted of tubules filled with slightly basophilic mucinous material. Histological and immunohistochemical examination confirmed the diagnosis of primary adenosquamous carcinoma (ASC) of the esophagus. This is the first report of primary ASC of the cervical oesophagus in a dog.