Dermatofibrosarcoma misdiagnosis

On Monday, I was told that I have Dermatofibrosarcoma after being told that it was just fat for 7 years.  Although, the prognosis for this type of cancer is good, I am terrified that it was overlooked for too long.  I am highly upset with my doctor.  The only way the cancer was discovered was because I decided that I wanted the gigantic "fat" mass removed.  Had it been up to my doctor, it would have still been there.  I am scheduled to see a general surgeon on Monday.  Has anyone had this type of experience (having mass for several years before it was discovered to be cancer) and what was the outcome?