Cancer

Site Map: Home Benign Growth Malignant Growth Progression Metastasis Dissemination Individual Effects Systematic Effects Response Diagnosis Evaluation Therapeutic Strategies Radiation Therapy Chemotherapy Other Ttherapies Prevention Causes Oncogenes Mutation Suppressor Gene DNA Repair Agents Chemicals Radiation Genetics Milestones Breast Cancer Bladder Cancer Brain Cancer Cervical Cancer Colorectal Cancer Esophageal Cancer Laryngeal Cancer Lung Cancer Liver Cancer Oral Cancer Ovarian Cancer Pancreatic Cancer Prostate Cancer Skin Cancer Stomach Cancer Uterine Cancer

Cancer is group of more than 100 distinct diseases characterized by the uncontrolled growth of abnormal cells in the body.

Cancer affects one in every three persons born in developed countries and is a major cause of sickness and death throughout the world. Though it has been known since antiquity, significant improvements in cancer treatment have been made since the middle of the 20th century, mainly through a combination of timely and accurate diagnosis, selective surgery, radiation therapy, and chemotherapeutic drugs.

Such advances actually have brought about a decrease in cancer deaths (at least in developed countries), and grounds for further optimism are seen in laboratory investigations into elucidating the causes and mechanisms of the disease. Owing to continuing advances in cell biology, genetics, and biotechnology, researchers now have a fundamental understanding of what goes wrong in a cancer cell and in an individual who develops cancer — and these conceptual gains are steadily being converted into further progress in prevention, diagnosis, and treatment of this disease.

Types of Cancer

Malignant tumours and benign tumours

Tumours, or neoplasms (from Greek neo, ''new''; plasma, ''formation''), are abnormal growths of cells arising from malfunctions in the regulatory mechanisms that oversee the cells' growth and development. When normally growing cells are transformed into undisciplined cancer cells, they divide and multiply and form masses of tissue known as tumours. As tumours grow, they invade and destroy nearby healthy tissues. If they gain access to the circulatory or lymphatic systems, tumours can migrate throughout the body, seeding in distant areas (a process known as metastasis). Tumours that grow and spread aggressively in this manner are designated malignant, or cancerous. Left unchecked, they can spread throughout the body and disrupt organs that are necessary to keep an individual healthy and alive.

Some tumours, however, remain localized to the area in which they arise and pose little risk to health. These tumours are called benign. Although benign tumours are indeed abnormal, they are far less dangerous than malignant tumours because they have not entirely escaped the growth controls that keep normal cells in check. They are not aggressive and do not invade surrounding tissues or spread to distant sites. In some cases they even function like the normal cells from which they arise.

Nevertheless, though they are incapable of dissemination, benign tumours do expand and can cause signs or symptoms of disease in an individual by replacing or impinging on an organ. In some cases benign tumours that compress vital structures can kill — for instance, tumours that compress the brainstem, where the centres that control breathing are located. However, it is unusual for a benign tumour to cause the death of an individual.

When the behaviour of a neoplasm is difficult to predict, it is designated as being of ''undetermined malignant potential,'' or ''borderline.''

'Malignant'' and ''benign'' are two important distinctions, but they are broad categories that comprise many different forms of cancer. A more detailed and useful way to classify and name tumours is by their site of origin (that is, the cell or tissue from which a tumour arises) and by their microscopic appearance. This classification scheme, though not followed with rigid logic or consistency, allows tumours to be categorized by a characteristic prognosis and therapy. Tumour nomenclature thus provides a means of identifying tumours and determining the best course of treatment.