Definition: uncontrolled growth of abnormal cells in the body Pathophysiology: The term cancer refers to a malignant tumor; a tumor that grows rapidly, isn’t encapsulated, invades local structures and tissues, is poorly differentiated, has rapidly dividing cells, and can spread distantly through blood vessels and lymphatics. These malignant tumors are made of tissue that overgrows and is independent of the body’s governing systems.
Cancers are termed according to the cell type from which they originate; those arising from epithelial tissue are called carcinomas, from ductal or glandular structures are adenocarcinomas, those from connective tissues have the suffix sarcoma, from lymphatic tissue are called lymphomas, and those from blood-forming cells are called leukemias. Others are from historical reasons such as Hodgkin disease and Ewing sarcoma.
Normal cells are governed by the body systems and have limited life spans but eventually cease growing and dividing then die. Cancer cells are usually immortal, having an unlimited lifespan, constantly growing and dividing. Cancer cells experience anaplasia, the absence of differentiation, causing disorganization in size and shape, mutating them from the normal cells of the body. Cancer can grow rapidly or slowly, progressing from normal cell tissue to neoplasm. Cancer forms a sequence of cellular and tissue changes progressing from dysplasia to carcinoma in situ and then to invasive cancer. Presence of anaplastic cells and loss of normal tissue architecture signify the development of cancer. This progression is easily seen in the squamous epithelium. The high rate of cell division, local mutagens, and inflammatory mediators all contribute to the accumulation of genetic abnormalities that lead to cancer. The mutation of these cells can happen at a chromosomal or genetic level and once it happens it can continuously happen as that originally mutated cell divides (cancer stem cell), making other cells like itself, forming a colony that continues to grow and sometimes can metastasize to other areas of the body through vasculature or lymphatic vessels.
Metastasis is the spread of cancer cells from where the original tumor is to distant organs and tissues throughout the body. This process is a defining characteristic of cancer and a major contributor to pain, suffering, and death from cancer. Localized cancer can often be cured by a combination of surgery, chemotherapy, and radiation but these therapies are commonly ineffective against metastasized cancer. This means cancer needs to be caught as quickly as possible before it has the chance to move to other areas. The invasion of cancerous cells causes tissue death due to the proteases secreted by cancer cells, along with taking over the tissues and organs. There are steps to the metastasis of cancer including (1) ongoing cancer proliferation; (2) digestion of tissue capsules and other structural barriers; (3) changes in cell-to-cell adhesions, making cancer cells more slippery and mobile; and (4) increased motility of individual tumor cells. The transition of cancer cells from their original tumor to other places relies on these four things, along with being able to survive in circulation, attach to an appropriate new microenvironment, and multiply to produce a new tumor with similar characteristics similar to that of the original cancer stem cell. Metastasis is a highly inefficient and difficult process as the cancer cells must surmount multiple physical and physiologic barriers in order to spread, survive, and proliferate and these distant locations. Cancer cells develop the ability to metastasize due to their increasing heterogeneity. They are incredibly diverse with many abilities giving them free reign to grow and move and take over. Cancer cells need vascular supply to grow and replicate so they find places to move that can supply them with that. Eventually these tumors form neovascularization, giving...
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