Cancer can affect your Shih Tzu just like it affects humans. And just like humans, the early signs of cancer may be difficult to spot or diagnose. Cancer is more common in older dogs, although it can also develop in younger dogs and puppies on rare occasions. Spotting the signs early can help you seek treatment for your pet, which may stop and reverse the progress of the cancer before it gets too far to be properly treated. Here are the ten early signs that your dog may have cancer.