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UT Arlington NURS 5315 - Cancer Lecture

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1 N5315 Advanced Pathophysiology Cancer Introduction Cancer is probably one of the most feared diseases that one can develop. It is very common. In some instances it is curable and in others it will cause death. The treatments for cancer are many and are based on genetics, the immune response, and involve cytotoxic agents. They often associated with many complications and can be very toxic. Cancer can begin almost anywhere in the body, in any cell. We have trillions of cells in our bodies which turn over quickly. When cancer develops, the normal cell life cycle is unregulated and the cells grow and proliferate causing cancer. Cancer cellular division is unregulated and malignant cells can invade local or distant tissues. Cancer cells differ from normal cells in a number of ways which allows their growth to be unregulated. One of these differences is that they are not specialized like normal cells. Normal cells grow from stems cells and are programmed to become a certain type of body cell with certain functions. Cancer cells are not like this and they are able to grow unregulated. Cancer cells ignore signals which instruct normal cells to stop cellular division and trigger apoptosis. They can avoid being detected by the immune system and at times may use the immune system to stay alive and grow. They can also prevent the immune system from killing cancer cells. Cancer Nomenclature The term cancer originated to describe the projections which stemmed from tumors. The term cancer is now used to describe malignant tumors. Cancer is defined by the National Cancer Institute as a disease in which abnormal cells divide without control and are able to invade other tissues. Benign tumors, are not considered cancerous. They are nonmalignant new growths. They do not spread locally or to distant sites, which means they are well encapsulated. Additionally, they are slow growing. They contain tissue which looks like the tissue of origin and therefore are said to be well encapsulated. They are named after the tissue of origin with the suffix “-oma”. Lipoma is a benign fatty tumor and a leiomyoma is a benign tumor of the smooth muscle of the uterus. The pathologic effects from benign tumors are from the space they occupy. While they do not invade tissues they may become large and compress normal tissue and inhibit blood. If they are located in the head and growing, the patient may have issues with increased intracranial pressure. Malignant tumors are rapidly growing and poorly differentiated. They do not look like the tissue of origin, they have rapid cell growth, and can metastasize to local tissues or distant sites. They are able to metastasize because they are not encapsulated. One of the many biologic characteristics of malignant cells is anaplasia, which is the loss of cellular differentiation. They are also pleomorphic which means that have variable shapes and sizes. Malignant tumors are named after the cell of origin but in addition to the “oma” they have the root words “carcino” or “sarco”. Tumors involving epithelial tissue usually have “carcinoma” plus the organ of origin. For example, hepatocellular Carcinoma is a malignant tumor of the surface epithelial tissue of2 the liver. Adeno- refers to the glandular epithelial tissue (deeper epithelial tissue or glands). An adenoma is a benign tumor of the glandular tissue whereas an adenocarcinoma is a malignant tumor of the glandular tissue. Carcinoma in Situ is a very early and preinvasive carcinoma of the glandular or squamous epithelial tissue. It has not broken thru the basement membrane. The basement membrane is a very thin layer of tissue which separates the epithelium (skin, respiratory tract, GI tract, etc), mesothelium (pleural cavity, peritoneal cavity, pericardial cavity etc), and the endothelium (blood vessels, lymph vessels) from the underlying connective tissue. Malignant tumors of the connective tissue have the root word “sarcoma”. Osteosarcoma is a malignant tumor of the bone. An osteoma is a benign tumor of the bone where as a chondrosarcoma is a malignant tumor of joint cartilage. Malignant tumors of the muscle are named using the specific muscle type “sarcoma” and “myo”. Uterine leiomyosarcoma is a malignancy of the smooth muscle of the uterus. Rhabdomyosarcoma is a malignancy of the skeletal muscle. Malignant tumors of nervous tissues are named based on the nerve cell type plus “blastoma”. A neuroblastoma is a malignancy of the nerve cell. A neuroma is a benign growth of a nerve cell. There are always exceptions to the rule. A lymphoma is malignancy of the lymphatic system, i.e. Hodgkin’s Lymphoma. Leukemia is a cancer of the WBCs, or leukocytes. Cancer Genetics This is a very complicated concept and it is not essential for you to know the complexities of cancer biology and genetics. I do want you to have an understanding of oncogene, tumor suppressor genes, telomeres and the BRCA gene. Proto-oncogenes produce proteins which regulate cellular proliferation. Cancer cells contain what is referred to as oncogenes which are proto-oncogenes that have mutated. Oncogenes function independent of normal regulator cellular mechanisms, thus the cancer cell proliferates. Oncogenes also provide a cancer cell with the ability to secrete growth factors which stimulate their own growth. This process is known as autocrine stimulation. In breast cancer, the oncogene human epidermal growth factor receptor 2 (HER2) is responsive to low levels of epidermal growth factor and this stimulates the breast cancer growth. This receptor is the target of some drugs used to treat breast cancer known as HER2 receptor inhibitors. Many genetic events activate oncogenes. The events include point mutations, translocations, and gene amplification. The inactivation of tumor suppressor genes contributes to the unregulated growth and proliferation of cancer cells. In normal physiology they are responsible for controlling cellular proliferation. They stop cell division in damaged cells and prevent mutations. There are two tumor suppressor genes in each cell and for their effects to be halted both genes must be turned off by the cancer. Tumor suppressor genes are known as anti-oncogenes. The p53 tumor suppressor gene produces the p53 protein that is responsible for monitoring cellular stress and activating the caretaker genes. These genes maintain the integrity of the genome. They produce proteins


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