What is cancer?
Cancer is a disorder of cell growth (uncontrolled cell division) that results in an abnormal mass of tissue (tumor) without a purpose. The growth exceeds that of normal tissue, is un-coordinated and persists after the cause has gone. There are many different types of cancers.
A few definitions
“Cancer” is the Latin word for ‘crab’ and the name describes the way the cancer adheres to adjacent tissues. Cancer is also known as “malignant neoplasia”. Malignant means “life threatening”, and neoplasia is Greek for “new growth”. The new growth is called a “neoplasm”. Not all neoplasms are malignant cancers. In fact, most are not life-threatening and are referred to as “benign”. The word “tumor” is Latin for a swelling. Tumors include swellings that are due to non-neoplastic causes. “Oncology” is the study of neoplasia.
Note that in strict medical terminology ‘cancer’ is used for malignant neoplasia but that in general usage it is often used as a broader term encompassing benign and malignant tumors.
What causes cancer?
Cancer is essentially the result of non-lethal genetic damage to cells (mutations in the DNA genome). Causes of such mutations include radiation, chemicals, hormones and infections. Some damage to cellular DNA is a daily “wear and tear” event but all mammals have many safeguards to prevent or repair such damage. Nonetheless, such protective mechanisms are not flawless. In some individuals there are even defects in such defences, resulting in a higher than expected prevalence of cancer. Some of those defects in protection can be inherited and in purebred dogs this can result in inherited predispositions to cancer development. In other instances it is excessive injury. The mutated DNA upsets the normal regulation of cell growth allowing uncontrolled and careless growth of the “altered” cells that no longer obey the rules governing coordinated cell activity.
