Pathophysiology – Cancer

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 them access into the venous blood.

Not only does the new vasculature allow the cells to grow and divide, it also allows for cancer cells to metastasize into the blood stream and lymphatic vessels. This makes taking over other tissues even easier and explains why one cancer can lead to another. Renal cell carcinomas are adenocarcinomas arising from tubular epithelium. Clear cell, granular, and spindle tumors can be found in the kidney. Tumors in the kidney usually occur unilaterally and 25-30% of patients with renal cancer present with metastasis due to the amount of circulation through the kidneys.

Lung cancers (bronchogenic carcinomas) arise from the epithelium of the respiratory tract and are the number one cancer killer in the world; the most common cause being cigarette smoking due to carcinogens in the tobacco smoke. Carcinogens along with genetic predisposition to cancers and genetic abnormalities make cancer easy to grow and spread. The bronchial mucosa suffers multiple carcinogenic “hits” because of repetitive exposure to carcinogens and eventually the epithelial cell changes into a carcinoma and becomes invasive then progresses into surrounding tissue and metastasizes to distant sites.

There are two main types of brain cancer. Primary brain cancer starts in the brain. Metastatic brain cancer starts somewhere else in the body and moves to the brain. No one knows the exact causes of brain tumors. Doctors can seldom explain why one person develops a brain tumor and another does. Any brain tumor is inherently serious and life-threatening because of its invasive and infiltrative character in the limited space of the intracranial cavity. Cancer of the small intestine, a rare cancer, is a disease in which cancer cells are found in the tissues of the small intestine.

The most common cancerous tumors of the small bowel include adenocarcinoma, lymphoma, sarcoma, and carcinoids. All these tumors have the potential to invade the bowel wall, spread into adjoining lymph nodes, and move to distant organs. Cancer is a multifactorial disease. Risk factors include: chemicals, environmental chemicals, genetics, hormones, infectious agents, radiation, sunlight, tobacco, weight, and physical activity. Psychological stress can also be a risk factor for cancer. Elderly are more inclined to have cancers but children and adults are affected also. Signs & Symptoms: * Physical pressue.

* Obstruction * Loss of normal function * Pressing on nerves * Secretion of bioactive compounds Renal Cancer: * Hematuria * Dull and aching flank pain * Palpable flank mass * Weight loss * Fatigue * Intermittent fever * Anemia * Hypertension Lung Cancer: * Coughing * Chest pain * Sputum production * Hemoptysis * Pneumonia * Airway obstruction * Pleural effusions Brain cancer: * Headache * Migraine * Dizziness * Behavior changes * Vomiting/nausea * Stiffness of the neck * Neurological dysfunction GI cancer: * Nausea * Bloating * Loss of appetite * Fatigue * Weight loss * Iron deficiency anemia.

Diagnostic procedures: biopsy, radiography, sputum analysys, urinalysis, tumor antigen-testing, screening tests, immunohistochemical strains, fly cytometry, electron microscopy, chromosome analysis, and nucleic acid-based molecular studies, endoscopy, CT scan Staging cancer is the determination of the size and degree to which a tumor has invaded or spread. Stage one is cancer confined to the organ of origin, stage 2 is locally invasive cancer, stage 3 is cancer that has spread to regional structures such as lymph nodes, stage 4 is cancer that has spread to distant sites Common Treatments:

Chemotherapy, radiation, or surgery References: American Cancer Society. (2013). Retrieved from http://www. cancer. org/ Dugdale, D. (2010). Retrieved from U. S. National Library of Medicine website: http://www. ncbi. nlm. nih. gov/pubmedhealth/PMH0002267/ McCance, K. L. , Huether, S. E. , et al, S. E. , et al, S. E. , & et al, S. E. (2010). Pathophysiology: The biologic basis for disease in adults and children. (6th ed. ). Maryland Heights, Missouri: Mosby.

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