Cancer is fatal disease notorious for the number of people that have fallen victim to it. In 2012, statistics showed that approximately 8.2 million people had their life taken by cancer. But what really is this disease and why does it affect so many people? In short, cancer is an out of control growth of cells that do not die. Cancer cells have a lack of contact inhibition. This means that instead of ceasing to divide as a normal cell would, they continue to divide even if normal cells come in contact with them. This uncontrollable spreading typically results in the formation of a tumour. Anaplasia is a term that refers to the lack of differentiation in neoplastic, or tumour, cells. The most basic definition of anaplasia means “to form backward,” which implies that these once well-developed cells eventually degenerated to form undifferentiated cells. Benign tumours are usually well-differentiated but cancerous tumours typically lack this differentiation. Cancer tumours also undergo vascularization in which blood vessels form to feed the tumour oxygen and nutrients. The process of vascularization is controlled by chemical signals in the body that control the creation, and reparation of blood vessels. This not only enables the tumours to grow and invade neighbouring tissue, but it also spreads throughout the body and forms other groups of cancer cells called metastases. Metastatic cancer refers to when the cancer has spread from its primary site to a secondary site around the body.The cause of cancer can be contributed to a myriad of different factors, both genetic and environmental. Environmental factors can range from direct or secondhand cigarette smoke, overexposure to UV light, or certain harmful chemicals, to an unhealthy diet, excessive alcohol intake, or simply a lack of physical activity. These substances cause the initial mutation in DNA and therefore the process that starts cancer due to these factors is called initiation. Proto-oncogenes are the genes that produce proteins and encourage the cell to go through the cell cycle, and divide. These genes promote cell development, but also the development of cancer. The mutated form of proto-oncogenes are called oncogenes. If the cell is exposed to radiation or other harmful chemicals, the DNA might break. When the pieces try to reconnect, they might join incorrectly and cause the production of an oncogene. Oncogenes act like “on switches” that encourage the cell to grow and divide and they act as a promoter in carcinogenesis. Once this oncogene is created, more altered proteins can be produced causing the cell to alter its shape, size and behaviour. As the cancer cell divides, each cell will possess an identical oncogene and thus, the cancer begins to spread and form tumours. Special genes named “tumour suppressor genes” prevent a cell from growing abnormally, however, the absence of these genes gives rise to the rapid growth of abnormal cells. From here, cancer can metastasize around the body and spread the cancer. Cancer cells possess some considerable abnormalities in comparison to a healthy cell. Healthy cells contain a single nuclei, whereas cancer cells contain more than one nuclei. This nuclei is typically darker in colour too. Moreover, cancer cells have a small cytoplasm, very coarse chromatin and a slightly distorted shape. Aside from the environmental and genetic factors mentioned above, there are also some viruses that can bring about carcinogenesis. Human Papillomavirus, more commonly known as HPV, is one example. Certain types of HPV are known as the leading cause of cervical cancer. This virus can lead to the changing of normal cells on the surface, to cells with precancerous changes, also known as cervical intraepithelial neoplasia. HPV is known to infect epithelial cells that cover the inside and outside of one’s body. As the HPV enters the epithelial cell, the virus begins to make proteins. Two of these proteins, E6 and E7, impede on the functions of the cell that are typically used to prevent excessive growth, which cause the cell to grow in an uncontrollable matter to avoid cell death. For the majority of the time, the immune system can recognize these cells and kill them off. However, there are some cases where these cells are not destroyed and lead to continuous spreading of the infection. As the infected cells continue to grow and spread, they may develop genetic mutations that promote even more abnormal cell growth. This can eventually form a cancerous tumour.  Leukemia is a unique type of cancer that is the most famous in children. Rather than forming tumours in a certain part of the body, leukemia is a malignancy of blood cells that take a toll on the body’s immune system. These abnormal blood cells are produced in the bone marrow and are produced until the unhealthy cells override the healthy cells, causing the immune system to be unable to fight infections. The symptoms of leukemia include but are not limited to: pain in bones or joints, swollen lymph nodes, fever or night sweats, feeling weak and tired, easily bruising or bleeding, frequent infections, swelling of the abdomen, and weight loss or appetite loss. Like most cancers, the causes of leukemia is not fully known but there are some risk factors such as radiation exposure, smoking, exposure of certain chemicals like benzene, or even genetics. The survival rate for leukemia is around 70-80% due to some fantastic treatment methods like chemotherapy, radiation therapy, and bone marrow transplants. Although sometimes these causes can be unavoidable as in the case of genetics, there are some ways to prevent getting leukemia such as avoiding smoking, radiation exposure, and the particular chemicals that can bring about this disease. Over the years, scientists have been working hard to find a cure for cancer. While no universal cure has been discovered, there are some up and coming treatments that have been successful in their fight against cancer. One of these treatments includes the use of stem cells. Stem cells are an immature form of cells which are incredibly useful due to their potential to develop into different types of cells in the body. Stem cells can be found around different parts of the body such as adult bone marrow, adult blood, umbilical cords, and embryonic tissue. While the ethics of this form of treatment is often called into question, stem cells have been successful in clinical trials, especially in the fight against leukemia. In conclusion, cancer is a complex and destructive disease that is known to affect many people worldwide. Its causes are varied and the different forms cancer can take are numerous, but the development of its rapid cell growth is much the same. However, the fight against cancer is being met with many potentially successful treatment options that can hopefully one day lead to the cure for all cancer.