My dog has a bump on her shoulder that is getting bigger. At one time I was told it was just an "old dog bump" and not to worry about it,...

Hello! If it is getting bigger, I would definitely have a cytology done by the vet. What that means is they would take a needle and extract a few cells from the tumor and then send it off to the lab to have it evaluated. This will tell them if it is cancerous or not, and how imperative it is to remove it. If it is cancerous, I would recommend having it removed sooner rather than later. Even if it isn't cancerous (benign), since it is growing, it may benefit her to have it removed so it doesn't eventually impede her walking, etc. It is also much easier for the vet to remove while small rather than large, and the healing time for your pet would be quicker for a smaller tumor. 

I'm unsure if there is a way to send a photo through this site, but the only way to truly tell what exactly it is, is to have a cytology or biopsy done. Masses can come in all shapes, sizes, and colors and looks can sometimes be deceiving. The fact that it is growing is concerning. 

They should be able to do a cytology while she is awake since it only involves a needle. That will at least hopefully give you some answers to help make a decision on what to do next. Depending on the size of the tumor, if it is still pretty small and she is at high risk for anesthesia, they may be able to do a mild sedative and a local block if she allows that rather than being put fully under.

It looks fairly small still. I would see if they can do a local to remove if needed. Could just be a wart-like mass, but again the only way to know for sure is to have a cytology done. Masses like that tend to get irritated and infected.