Cancer

Cancer refers to disease caused by the malignant growth of a certain type of cells in the vertebrate body: epithelial cells. When rapidly dividing malignant cells form a solid mass, cancers are tumors, but when malignant cells circulate in blood, or cerebral spinal fluid, cancers may not make tumors. In cases, such as leukemia, for example, masses are not ordinarily present but many aspects of the disease are the same as when solid tumors are the primary and most obvious manifestation of cancer. That's because, in all cases of cancer, there is unbridled growth of malignant cells, and that means that much of the body's nutrition goes towards supporting abnormal rather than normal cells, that some or all of the functions of the normal body parts that have become cancerous are lost, and that the general resistance and vitality of a person is compromised by the excessive demands of the abnormal cells. When cancers are "early", they usually involve only a relatively small amount of abnormal growth, when they are both late and widely dissemated, they generally involve a much greater portion of the body. That's one reason why early and limited cancers less obviously impair health, unless they involve an organ such as the brain. Since it is early cancers that are most successfully treated, by and large, much of modern medicine has been devoted to finding means to diagnose malignancies early, and public health campaigns have promoted education of citizens to early warning signs of the various kinds of cancer.

Although the origin of cancer in an epithelial tissue is strictly required for the most technically accurate use of the term, cancer, the word is often used, even by physicians and hospitals, to include all the diseases directly caused by malignant tumors and cells. For example, malignant tumors called sarcomas arise from abnormal muscle-type cells, and since these tissues are derived from mesothelium rather than from epithelium, that word sarcoma is used rather than cancer to name the tumor. Still, cancer centers and specialists include treatment of sarcoma in practice, despite the fact that sarcomas and cancers differ in the medical classification of malignant tumors. In other words, all types of malignant tumors are sometimes referred to as cancers, and one type of these malignancies: epithelial malignancies, are, even more strictly, known as cancers.

This introductory article will give a brief description of what a malignancy is, and how cells are thought to become malignant. That understanding is important as a basis to comprehending the medical and surgical treatment of cancers, and effective practices in their prevention. After a general introduction to malignancies, major types of cancers (epithelial malignancies) are surveyed, with links provided for further information. The clinical emphasis is on human cancers, but references to cancers in other species of animals is also made. Although the frequencies and the aggresiveness of the various types of cancers vary according to species, generally, the basic biology of cancers is true for all species, including humans and domestic animals.

Oncology,Hematology and specialists who treat cancer

The two medical specialties that focus on malignancies are oncology and hematology. oncologists are physicians who are fully trained in Internal Medicine and have further training in the treatment of malignant tumors, primarily solid tumors. Hematologists are also physicians who are fully trained in Internal Medicine, in their case further training is in disorders of the blood, including the bone marrow, which produces blood cells. However, some types of cancers and other malignancies are equally the province of other specialists, because of the part of the body they affect, or because the treatments they require, are the focus of those particular specialties. So, for example, radiation oncologists, who are trained in the use of external beam radiation and other kinds of radiation treatments, and surgeons who are specialists in the areas of the body that the cancer affects, like the breast or larynx, are important in cancer care, and depending on the type and extent of the cancer, may be the main physician directing the cancer patient's care. For several decades, however, the notion of a "team approach" has been embraced in the treatment of cancer. A team approach offers the support of an entire group of professionals, including the physicians mentioned, nurses, social workers and others.