Abstract:
Primary lung cancer is rare in dogs and depending on the tumour stage and subtype, the
prognosis can be poor. In this report, we describe a 10 year-old female intact Yorkshire terrier that
presented progressive weight loss and chronic pain of unknown origin. Due to the poor condition
of the dog, it was subsequently euthanized. Post-mortem evaluation revealed a single large mass
in the left caudal lung lobe, with numerous pale, proliferative lesions of various sizes dispersed
throughout all the lobes. Additionally, a solitary skin mass was palpated on the mid-thoracic
body wall. Histopathological examination of the lung samples revealed multiple distinct, nonencapsulated,
expansive neoplastic epithelial cell proliferations with dense cellularity, exhibiting
growth patterns, ranging from papillary to micropapillary to solid, accompanied by central areas
of necrosis. In some areas, microvilli-like structures were observed on the luminal cytoplasmic
margins of the neoplastic cells. The histopathology of the skin mass closely resembled that of the
lung. Electron microscopy of the skin samples revealed regions containing cells resembling the
respiratory epithelium, along with cells exhibiting processes or microvilli indicative of cilia. The
diagnosis was pulmonary adenocarcinoma with cutaneous metastasis. This is the first report of a
canine with primary lung cancer that metastasized to the skin.
