Читать книгу Fundamentals of Cancer Detection, Treatment, and Prevention - Surya K. De - Страница 32

As mentioned earlier, cancer starts when gene mutations interfere with the normal, orderly process of cell division. Cells begin to grow uncontrollably without stopping, sometimes forming a mass of tissue called a tumor. Tumors can be cancerous or benign. As previously mentioned, a cancerous tumor is malignant, meaning it can grow large and extend to other locations of the body. A benign tumor can become larger over a period of time, but will not spread to other parts of the body.

Metastasis is the medical term for cancer that appears in a different organ than where it originated from. When this occurs, scientists say the cancer has metastasized. Other terms referring to metastasis are metastatic cancer and stage 4 cancer. Some types of cancer do not form a tumor, including leukemias, most types of lymphoma, and myeloma.

One of the first places cancer often metastasizes to is the nearest lymph node(s). A lymph node is a tiny, bean‐shaped organ that functions in the human body's defense against infection. Lymph nodes are located in clusters in different parts of the body, such as the neck, groin area, and under the arms. Due to lymph nodes being part of a system, which circulates about the entire body, called the lymphatic system, cancer cells that reach the lymph nodes can be further transported to other body areas.

Metastases to the bones, brain, liver, lymph nodes, and lungs are very common. Some cancers tend to spread to certain parts of the body. For example, unresolved breast cancer spreads to the bones, liver, lungs, chest wall, and brain, whereas lung cancer tends to extend to the brain, bones, liver, and adrenal glands. Prostate cancer mainly spreads to the bones. Colon and rectal cancers have the greatest chance of spreading to the liver and lungs.