My dog had some lumps on her belly that I was convinced were benign lipomas, but they turned out to be malignant mast cell tumors, so it's wise to have any lumps on your dogs checked sooner, rather than later. My girl Sadie (9 1/2 years old) has had three different surgeries now to remove mast cell skin tumors, but she has one in her anus that's inoperable, so she's also on chemotherapy with Chlorambucil to try to slow the tumors down. But I just noticed a new lump on her belly, so I suspect that we'll need to plan on another surgery in the not-too-distant future. But she's still a sweetheart and doesn't seem to be too bothered by the chemotherapy and is still enjoying life.