Lameness in a Dog Caused by Thoracic Wall Invasion by a Pulmonary Neoplasm

Summary A 12‐year‐old fox‐terrier dog presented with forelimb lameness of 3‐weeks duration. Ultrasonography revealed a mass within the thoracic wall and osteolysis of the left third rib. A squamous cell carcinoma was diagnosed by cytological examination of an ultrasound‐guided fine needle aspirate of this mass. As a result of the diagnosis of neoplasia, the dog was euthanatized. Necropsy revealed a solitary expansile mass within the left cranial lung lobe, and a mass within the adjacent thoracic wall. Thickening of the pleura between the two masses was visible, although adhesions were not present. Histology of both masses revealed a well‐differentiated squamous cell carcinoma. To the authors’ knowledge, this is the first detailed description of direct invasion of the thoracic wall by a canine lung tumour.