Hi -- We have had several dwarf hamsters and when I took one to the Vet for treatment, she said they often get cancer. We have had three out of our five dwarf hamsters have died from cancerous tumors which got bigger and bigger. Not much you can do, unfortunately. If you can just keep him or her comfortable (lots of comfy fluff -- we use cotton make-up pads which the hammy can shred itself) at least you can make your hammy's days more comfortable. Also remember that dwarf hamsters live a maximum of two years or so, so their lives are short.