EVERYDAY SCIENCE

Detailed explanation-1: -Tumors may be benign (not cancer) or malignant (cancer). Benign tumors may grow large but do not spread into, or invade, nearby tissues or other parts of the body. Malignant tumors can spread into, or invade, nearby tissues. They can also spread to other parts of the body through the blood and lymph systems.

Detailed explanation-2: -Stage I: The cancer is localized to a small area and hasn’t spread to lymph nodes or other tissues. Stage II: The cancer has grown, but it hasn’t spread. Stage III: The cancer has grown larger and has possibly spread to lymph nodes or other tissues. Stage IV: The cancer has spread to other organs or areas of your body.

Detailed explanation-3: -Carcinogenesis can be divided conceptually into four steps: tumor initiation, tumor promotion, malignant conversion, and tumor progression (Figure 17-1). The distinction between initiation and promotion was recognized through studies involving both viruses and chemical carcinogens.

Detailed explanation-4: -Carcinomas. A carcinoma begins in the skin or the tissue that covers the surface of internal organs and glands. Sarcomas. A sarcoma begins in the tissues that support and connect the body. Leukemias. Leukemia is a cancer of the blood. Lymphomas.