My dog has many fatty tumors, most of them appeared quite rapidly and then just stayed put. Keep you eye on them, and any that seem to grow, get them removed. My dog had one under his armpit that continued to grow, and I didn't want to have surgery done as he is 12 years old, but finally it was really interfering with his movement, not to mention just ugly looking, so I had the surgery done. Alas, it had turned from a benign fat tumor to a Grade One sarcoma. Fortunately the vet said grade one tumors are so slow growing, and rarely metatisis, so he feels removing it was the best option. My dog tolerated the surgery well and is moving much, MUCH better, back to enjoying his daily walks.

PLEASE, if there are any changes in any lumps or bumps, get them checked or removed. Better to do it when the lumps are small and not cancerous.