Q. My dog has a golf ball mass on her side
A. It is impossible to understand what kind of mass it is just based on this description. Sometimes a consultation is not enough to understand either, and it is necessary for your vet to send a fine needle aspirate or a biopsy to a lab to get more information about the cells that constitute the lump. Fine needle aspirates are not too invasive, however it can be tricky sometimes to get a useful sample. I would recommend a visit to your vet in order to put your mind at rest and to be able to start treatment promptly if necessary. I hope this helps !