Cancer is a disease that develops when some of the body’s cells begin to grow out of control and form growths called tumors. These abnormal cells may also spread into nearby tissues and lymph nodes. When this happens, the cancer is considered malignant, meaning it can invade and destroy healthy tissue. There are many different types of cancer, and each type requires a unique treatment plan. Cancer treatments include surgery, radiation and chemotherapy. The most common treatment is surgery, which involves removing the mass of cancerous cells from the body. Radiation and chemotherapy are treatments that use high-energy rays or drugs to kill cancerous cells. These treatments can also cause side effects, such as hair loss and nausea.
Some cancers may be more likely to recur after treatment than others. Therefore, doctors recommend following a routine of regular screening tests to catch cancers early. These tests, including mammograms, colonoscopies and prostate exams, can help prevent or detect cancer before it causes symptoms.
Most multicellular organisms have strict limits on cell proliferation. Cells that are no longer needed die or undergo a process known as programmed cell death, or apoptosis. As a result, the populations of cells in normal tissues are packed together at much lower densities than in cancerous cells, which have uncontrolled growth rates.
This uncontrolled growth of cancerous cells is one of the hallmarks of cancer that has been recognized since ancient times. In modern times, molecular biology has revealed how cancers develop through a series of genetic mutations that drive their development and progression (2-4).
The heritable variation in these mutations is what leads to the struggle for survival that defines natural selection. The resulting adaptations of cancer cells are what makes the disease so dangerous and challenging to treat.
As a cancer progresses, different groups of cells evolve to fill distinct ecological niches in the tumor microenvironment (5-6). These adaptations are what make cancer resistant to the effects of therapy. These phenotypic differences among cancer cells are the basis for what is known as intratumoral heterogeneity (7,8).
The emergence of these adaptations is a defining feature of cancer, and it is what distinguishes it from other diseases such as inflammatory bowel disease or viral infections. Cancer is the only disease that has these characteristics, a unique feature that can be used to identify cancers when they are first diagnosed.
Cancer can be prevented by practicing a healthy lifestyle, eating well and avoiding tobacco or excessive alcohol use. Exercise is also important – at least 150 minutes of moderate or 75 minutes of vigorous activity each week is recommended. In addition, doctors recommend avoiding sun exposure and limiting how much red meat you eat. Up to 50% of cancers are preventable, according to research. (1)