9 year old Rottweiler

Discussion

The thoracic nodule was difficult to localize on the standard projections. Visibility of an extrapleural sign depends on catching it perpendicular to the x-ray beam. Centering over the lesion and collimating can help, as can rotating the dog to either side.
The humeral lesion is distal to the metaphysis, where most osteosarcomas originate. This raises the possibility of it being a metastatic lesion from another site, or a fungal lesion. The biopsy proved osteosarcoma in this case.

This radiograph was taken centered over the pulmonary lesion. It shows the rib has lytic and expansile components, and that the rib mass is protruding into the thorax. This is most likely metastatic disease from the osteosarcoma. It is a very nice example of an extrapleural sign, where the mass has a broad base and extends to the pleural surface.