Can I have a tumor of the gallbladder?

Yes. Both benign and malignant tumors can develop within the gallbladder. A tumor is often found as a polyp on ultrasound; although an overwhelming majority are benign, we recommend removing the gallbladder if the polyp is 1 CM or larger. Cancers typically present incidently during gallbladder removal or at advanced states, due to their propensity to spread to the liver.
Depends. On your symptoms. Tumors of the gallbladder do occur, although they are relatively rare.