Wendi, my sheltie is going on 10 and has fatty tumors on various parts of her body. Our vet said they were all nothing to worry about
but the one on her elbow kept growing so much that she was uncomfortable. He did a needle biopsy which told him that it was releasing toxins into her system. I had noticed the lethargy but figured it was due to the rescue pup we were fostering at the time. She doesn't have a motherly instinct in her body!
ANYHOW...he took that tumor off and her entire attitude changed. This tells us that we need to watch the other tumors carefully, esp the one at the top of her spine. I check her body daily just to see what's up with 'em. Have no idea what will happen next.