scar tissue?

Question
Hello,

I apologize if this isn't considered a "skin" question and you can certainly disregard the question if need be. I am asking about the issue of scar tissue and whether or not this is a common problem but am not really sure if this can be classified as such.

About 3 years ago I took my dog to the vet to have a fatty tumor removed from his shoulder. According to the vet the tumor had grown through the muscle in his shoulder and it was imperative that we have it removed before it got larger. Surgery went fine however there was a lot of swelling in his shoulder. About a year after the surgery and routine follow ups I took him back because I was concerned about the size of his shoulder. The vet assured me it was just scar tissue. Now that it has been 3 years or so after the surgery the "scar tissue" seems to have gotten even bigger. I was petting him yesterday and noticed that the swelling is now around his neck. Is it safe to say that the tumor has returned? I am scheduled to take him in this week but am curious to know if this is a common issue post surgery? He doesn't appear to be in pain and is still very active but lately, every once in a while, I notice that the mass is slowing him down. Any information is appreciated.

Thank you

Answer
There are many "fatty tumors" that may not be fat.  Did they have the tissue tested to see if it really was fat?  Lipomas generally do not return once they are removed, but if the tumor was a liposarcoma, a mast cell tumor or another tumor called a hemangiopericytoma, they can return in the same place or worse.