Malignancy, muh LIHG nuhn see, is the tendency of a disease to be severe and possibly cause death. It most frequently refers to a malignant tumor, or cancer, in contrast to a benign (mild) tumor (see Cancer; Tumor). Benign tumors remain in one part of the body and grow slowly. Malignant tumors can invade surrounding normal tissue, or spread to distant organs of the body through the blood, a process called metastasis. Malignant cells often resemble the normal cells that they originate from, but they have unique characteristics that make them malignant. Many people say malignancy when they mean cancer.