This Condition Guide provides an overview of cancer. Cancer is the term used to describe the uncontrolled growth of abnormal cells that have changed or mutated from normal cells. As cancer cells grow and multiply they form a mass of cancerous tissue called a malignant tumor. A malignant tumor can invade and destroy surrounding healthy tissue. When the cancer spreads from the original tumor site to other parts of the body, the process is called metastasis.
When normal cells grow rapidly and mutate, a distinct mass of abnormal tissue forms. This mass is called a tumor. A benign tumor is not cancerous; a malignant tumor is cancerous. A malignant tumor is often a fast-growing tumor. The tumor grows and replaces the cells of healthy tissue. Cancers can spread to other parts of the body, including organs, tissue, and bone. When cancer spreads to a site beyond the initial tumor, it is called metastasis. With metastatic cancer, cancer cells destroy healthy tissue as the cancer spreads. Cancer growth prevents vital organs from functioning normally and can lead to organ failure.
Cancers can be sarcomas or carcinomas. Sarcomas are malignant tumors, or cancers, of connective tissues. Carcinomas are malignant tumors, or cancers, of the cells that cover the surface of the body, produce hormones, and make up glands. Carcinomas include the most common cancers that include those of the skin, lung, colon, breast, prostate, and thyroid gland. In addition, cancers of the blood and blood forming tissues are classified as leukemias and lymphomas. Lung cancer is the most common cause of cancer-related death in the United States. Women are most often affected by breast cancer, lung cancer and colon cancer, whereas cancers of the prostate, lung, and colon are the most common in men.
Although the cause of many malignant tumors remains unknown, abnormal regulation of cell division seems to play a role in the development and metastasis of cancer. Risk factors for cancer include family history, chromosomal abnormalities, environmental factors (radiation, sunlight, tobacco), diet, and certain viruses. Symptoms of most cancers include fever, chills, night sweats, decreased appetite, fatigue, and malaise. Tissue biopsy and blood tests can help diagnose cancer.
