7.11: Cancers
Cancer refers to a type of disease characterized by the uncontrollable growth and spread of cells that serve no physiological function in the body. Healthy cells have a predictable number of divisions they can undergo to make new cells before they program their own death (cell apoptosis). Cancerous cells have genetic mutations and/or epigenetic changes that cause excessive reproduction and prevent their programmed destruction. These cells can form solid clumps, called neoplasms or tumors. Cancers as a group are often referred to as malignant neoplasms in epidemiology.
Tumors or neoplasms are clumps of cells that serve no physiological function, and can start invading nearby tissues or putting pressure on other bodily structures. Benign tumors are not cancerous - they are much slower-growing and don’t tend to spread. However, benign tumors can still cause problems if they begin to put pressure on nearby physiological structures. Malignant tumors are cancerous: they grow more rapidly, grow their own network of blood vessels to bring them nutrients, and invade nearby connective tissues and lymph nodes. Cancerous cells also break free from the neoplasm and spread through the lymphatic system or bloodstream to other parts of the body - a process called metastasis . Some cancers have no solid tumors to begin with, but instead these malignant cells proliferate in the bloodstream or lymph system. Although cancers have these common characteristics, each cancer is a separate disease, named by the tissue and organ the cells originated in ( What Is Cancer? , 2022). Different cancers have varied causes, risk factors, and treatments.