Pathogenesis of Cancer

Cancer is the uncontrolled growth and spread of abnormal cells in the body. Cancers (malignant neoplasms) can arise from virtually any tissue and are usually named by the anatomic site of origin. Examples include breast cancer, prostate cancer, colon cancer, and lung cancer, the four cancers responsible for the majority of cancer deaths in many developed nations such as the United States. Cancer cells have the ability to divide continuously, invade other tissues, and spread (metastasize) to other organs through the blood and lymph. These primary features (uncontrolled cell division, invasion of contiguous tissue, and metastasis) distinguish cancerous growths from noncancerous (benign) cellular growths, the latter being self-limiting with no ability to invade tissue or metastasize. Cancer is further defined according to the cell of origin based on microscopic examination by pathologists. Adenocarcinomas arise from the cuboidal epithelial cells that line the ducts of glandular tissue (e.g., adenocarcinomas of the breast, prostate, colon, or lung). Squamous cell carcinomas arise from the flat pavement cells that cover the skin and line portals of entry or exit in the human body (e.g., squamous cell carcinomas of the oral cavity, upper airways, esophagus, uterine cervix, urinary tract, or anus). Sarcomas arise from connective tissue (fibrosarcoma) or bone (osteosarcoma). Malignant gliomas arise from glial cells that provide vital support to neurons in the central nervous system. Adenocarcinomas, squamous cell carcinomas, sarcomas, and gliomas are solid tumors, as opposed to cancerous growths of immune cells that arise in the bone marrow (leukemias) or the lymph nodes (lymphomas) and circulate in the blood or the lymphatic system. evolution of cancer