Pets commonly develop lumps and bumps as they age. Certain breeds, of dogs such as Weimaraners, are especially prone to this problem. Unfortunately, some doctors don't appreciate the seriousness of these lumps and bumps and diagnose them as "fatty tumors" or "cysts" simply by looking at and feeling the tumor. While it is true that most lumps and bumps are benign fatty tumors and not cancerous, there is no way to accurately tell this by look or feel. All lumps and bumps should be considered cancerous until proven otherwise. Deciding whether a tumor is cancerous or benign is fairly easy and involves inserting a tiny needle into the tumor and aspirating cells from it, which are then examined in a lab. In most cases, there's absolutely nothing to worry about.
However, in those instances in which the tumor is cancerous, early diagnosis will allow a doctor to promptly treat, and often cure the disease. One of the most important things I learned from my cancer teachers and veterinary schools is "Don't watch cancer grow." Investigating all lumps and bumps that are large enough to be aspirated when first noticed is the most important thing pet owners can do to keep their pets safe and healthy.