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A neoplasm is an abnormal new growth, or tumor, and a malignant, or cancerous, neoplasm is usually one that grows in a relatively rapid, disorganized manner and has a tendency to spread. The mode of spread can involve directly invading the surrounding tissue, or traveling via the blood or lymphatic system to reach other parts of the body, a process known as metastasis. A malignant neoplasm is more commonly called a cancer, and the study of both benign, or non-cancerous, and malignant neoplasms is known as oncology.
Neoplasms are lumps of abnormal cells arising in any part of the body. When normal cells grow and multiply excessively, as they do in a swollen gland, or when a muscle is built up and strengthened, this is not regarded as a neoplasm. If cells become abnormal, they either change into a different, usually more primitive, kind of cell, or they become generally very disordered, showing odd shapes, sizes and internal structures. It is thought that damage to the genetic material inside a cell causes such changes and, once the process has begun, just one abnormal cell can divide and multiply to eventually form a neoplasm.
While a benign neoplasm normally has a containing capsule around it, grows slowly and does not invade surrounding tissues or spread, a malignant neoplasm grows quickly, developing its own blood supply and pushes its way through normal body tissues causing damage and invading its surroundings. Some cells from a malignant tumor may make their way into a blood vessel and metastasize, which means they are carried in the bloodstream to different areas of the body. Here, the cells can grow into secondary tumors, or metastases, which cause further destruction as they enlarge and spread through tissue.
Another way in which the cells of a malignant neoplasm are able to metastasize is by entering a vessel that is part of the lymphatic system. Like the blood circulatory system, the lymphatic system consists of a network of pipes, or vessels, that run throughout the body. The lymphatic system contains a lot of white blood cells and is involved in fighting infection as part of the immune system. It contains numerous lymph nodes, or glands, which can become swollen when a person is ill. Malignant cells may end up growing inside a lymph node, which is why the nodes nearest to a malignant neoplasm sometimes become enlarged when someone has cancer.
The discovery of a malignant neoplasm usually leads to a referral to a doctor specializing in cancer, known as an oncologist. There are many different kinds of cancer which, although they will share the general characteristics of malignant neoplasms, all behave slightly differently and respond to different treatments. The most common treatments involve surgery, radiotherapy and chemotherapy, and the outlook depends on the type of cancer and the degree to which it has spread.