General Information About Cancer

The technical term for Cancer is malignant neoplasm, a class of diseases in which a group of cells displays uncontrolled growth (division beyond the normal limits), invasion (intrusion on and destruction of adjacent tissues), and sometimes metastasis (spread to other locations in the body via lymph or blood).  What differentiates these three malignant properties of cancers from benign tumors is that benign tumors are self-limited, and do not invade or metastasize. Although most cancers form a tumor some, like leukemia, do not. There is a specific branch of medicine concerned with the study, diagnosis, treatment, and prevention of cancer called oncology.

Cancer is very insidious and may affect people at all ages, even fetuses, but the risk for most varieties increases as a person’s cells age.  It is a known fact that cancer causes about 13% of all human deaths.  According to the American Cancer Society, 7.6 million people died from cancer in the world during 2007.  In fact, cancers can affect all animals.

Almost every cancer known is caused by abnormalities in the genetic material of the transformed cells.  There are many possibilities from which these abnormalities may arise.  They may be due to the effects of carcinogens, such as tobacco smoke, radiation, chemicals, or infectious agents.  There are other cancer-promoting genetic abnormalities which may be randomly acquired through errors in DNA replication, or they are inherited, and thus present in all cells from birth. The inheritability of cancers is usually affected by complex interactions between the carcinogens and host's genome. As the field of cancer is studied and new discoveries are made through the human genome, new aspects of the genetics of cancer pathogenesis, such as DNA methylation, and micro-RNAs are increasingly recognized as important.

Two general classes of genes are typically affected by genetic abnormalities found in cancer:  Cancer-promoting oncogenes, which are typically activated in cancer cells, giving those cells new properties, such as hyperactive growth and division, protection against programmed cell death, loss of respect for normal tissue boundaries, and the ability to become established in diverse tissue environments. Tumor suppressor genes then become disactivated in cancer cells, resulting in the loss of normal functions in those cells, such as accurate DNA replication, control over the cell cycle, orientation and adhesion within tissues, and interaction with protective cells of the immune system.

A cancer diagnosis usually requires the histologic (the minute structure of animal and plant tissues as discernible with the microscope) examination of a tissue biopsy specimen by a pathologist, even though there may be initial indication of malignancy, which can be symptoms or radiographic imaging abnormalities. Depending on the specific type, location, and stage, most cancers can be treated and some even cured. Once diagnosed, cancer is usually treated with a combination of surgery, chemotherapy and radiotherapy.  Treatments are becoming more specific for different varieties of cancer as research and knowledge develop.

On another front, there has been significant progress in the development of targeted therapy drugs that act specifically on detectable molecular abnormalities in certain tumors, and which minimize damage to normal cells. The prognosis of cancer patients is most influenced by the type of cancer, as well as the stage, or extent of the disease. In addition, histologic grading and the presence of specific molecular markers can also be useful in establishing prognosis, as well as in determining individual treatments.