CANCER AND MALIGNANT GROWTH
1. Cancer is a disease of the body’s cells. It occurs when cells in the body become abnormal and grow out of control. A change which makes the gene faulty is called a mutation. Some special genes, called control genes, instruct the cell to copy its genes correctly, and to divide in an orderly manner. They stop controlling cell division, which is cancer.
humans, but most pose little risk to their host because they are localized and of small
size. The surface interaction molecules that hold tissues together keep benign tumor cells, like normal cells, localized to appropriate tissues. A fibrous capsule usually delineates the extent of a benign tumor.
3. Malignant tumor: In contrast, the cells composing a malignant tumor, or cancer,
express some proteins characteristic of the cell type from which it arose, and a high
fraction of the cells grow and divide more rapidly than normal.
4. Some malignant tumors remain localized and encapsulated, at least for a time; an
example is carcinoma in situ in the ovary or breast.
5. Most, however, do not remain in their original site; instead, they invade surrounding tissues, get into the body’s circulatory system, and set up areas of proliferation away from the site of their original appearance.
6. The spread of tumor cells and establishment of secondary areas of growth is called metastasis; most malignant cells eventually acquire the ability to metastasize.
7. Thus the major characteristics that differentiate metastatic (or malignant) tumors from benign ones are their invasiveness and spread.
Comments
Post a Comment