The process by which normal cells develop into cancer cells is called malignant transformation. In the last 40 years in the U.S., the cancer death rate has declined in women and increased in men. If any one of these signs is observed, it should be brought to a physician's attention without delay. Etiology Unregulated, disorganized proliferation of cell growth may be stimulated by various chemicals, viruses, and physical agents such as ionizing radiation and ultraviolet light. Ironically, cytotoxic agents used to treat cancer may cause it.
Several agents are specific carcinogens, notably the chemicals contained in tobacco products.
Although some of these techniques and devices may demonstrate an increase in the size or change in the shape of an organ, such alteration may be due to either a benign or a malignant growth. The most effective screening tests to detect cancers in the symptomless stage are those for cancer of the uterine cervix, breast, and prostate. Tests for cancer of the ovary, lung, and colon are being researched. Metastatic cancer in which it is not possible to determine the site of the primary malignancy frequently involves adenocarcinoma, melanoma, lymphoma, sarcoma, or squamous carcinoma. Even though the prognosis is poor for patients with these types of malignancies, the response may be improved when the cell type is specifically identified.