Cancer

Cancer

When normal cells are damaged beyond repair, they are eliminated by apoptosis. Cancer cells avoid apoptosis and continue to multiply in an unregulated manner.Cancer is a class of diseases characterized by uncontrolled cell division and the ability of these cells to invade other tissues, either by direct growth into adjacent tissue (invasion) or by implantation into distant sites (metastasis). This unregulated growth is caused by damage to DNA, resulting in mutations to genes that control cell division. Several mutations are required to transform a normal cell into a malignant cell. These mutations are often caused by chemicals or physical agents called carcinogens, the best known being tobacco smoke. Some mutations can be inherited.
Tumor ("swelling" in Latin) is a more general term that describes an abnormal mass of tissue. Tumors can be malignant or benign. Cancer is synonymous with malignant tumor.
The word cancer is not used in Medicine as it lacks accuracy, but remains the common name for this group of diseases in most languages. Malignant tumors are classified as such:
Carcinoma: malignant tumors derived from epithelial cells. This group represent the most common cancers, including the common forms of breast, prostate, lung and colon cancer. Lymphoma and Leukemia: malignant tumors derived from blood and bone marrow cells Sarcoma: malignant tumors derived from connective tissue, or mesenchymal cells Glioma: tumors derived from brain cells germ cell tumours: tumors derived from germ cells, normally found in the testicle and ovary Choriocarcinoma: malignant tumors derived from the placenta Cancer can cause many different symptoms, depending on the site and character of the malignancy and whether there is metastasis. Usually, cancer is painless at an early stage. A definitive diagnosis usually requires the histologic examination of tissue by a specialized physician called a pathologist. This tissue is obtained by biopsy or surgery. Once diagnosed, cancer is usually treated with surgery, chemotherapy and/or radiation.
If untreated, most cancers eventually cause death; cancer is one of the leading causes of death in developed countries. Most cancers can be treated and many cured, especially if treatment begins early. Many forms of cancer are associated with environmental factors, which may be avoidable. Cigarette smoking leads to more cancers than any other environmental factor.