The word “cancer” covers a very diverse group of around 200 illnesses. They have different causes, strike different organs and tissues, and require very specific tests and treatment solutions. There are, however, some aspects common to all cancers. To use a metaphor, we can say that at a certain point a cell in the body “goes rogue”— it loses certain properties and develops new ones —and starts to multiply uncontrollably.
A cell turns from normal to cancerous through a number of steps and a gradual accumulation of genetic, functional and morphological abnormalities.
Every cell contains master genes, whose job is to prevent a “misbehaving” cell from surviving and perhaps leading to a tumor. For tumor growth to be triggered, these genes too must malfunction. When something is wrong in the mechanisms that control replication, the cells divide when they shouldn’t, and generate a huge number of new cells with the same defects. Healthy cells end up being overwhelmed by the faster-growing cancerous cells.
Cells of benign and malignant tumors both proliferate abnormally; the fundamental difference is that only those of a malignant tumor—after their genes have accumulated additional defects —will break off, invade nearby tissues, and migrate from the organ where they were first located to colonize other parts of the body.
It is now well known that cancers are caused by a combination of internal and external factors. Internal factors originate from cells of the body and, in some cases, can be passed down to offspring. They include genetic mutations, hormones, immune system function, etc. and usually cannot be modified. Conversely, external factors found in the living and working environment (e.g. infectious agents, chemicals, ionizing and non-ionizing radiation) or controlled by a person’s lifestyle (diet, exercise, smoking, etc.) can be modified through prevention programs whose effectiveness has been widely demonstrated.