Tumor vs cancer. A tumor is an excessive growth of tissue. It can be benign (not dangerous) or malignant (dangerous because it can spread). Cancer is caused by malignant tumors.
Mets. Tumors refer to any lump of mass, that can be benign (will grow locally) or malignant (will spread to other parts of the body). Benign tumors can be cured by surgery but malignant tumors often require chemo-radiation for control. Cancers are malignant tumors that arise from the lining layer of organs or glands.