[header] How to diagnose canine cancer [title] Look for lumps on the skin. [step] The most important thing you can do is to be alert for changes in your dog. This includes paying attention to lumps, like watching for the growth of a new lump on the skin, the enlargement of an existing lump, and a change from a lump not bothering the dog to becoming angry-looking or itchy. 
[title] Watch for unexplained weight loss. [step] Another common symptom of canine cancer is weight loss.