Unit 5.1: Definition of CancerGeneral Definition of Cancer Show The American Cancer Society (ACS) defines cancer as a group of diseases characterized by uncontrolled growth and spread of abnormal cells. If the spread is not controlled, it can result in death. A cancer cell is a cell that grows out of control. Unlike normal cells, cancer cells ignore signals to stop dividing, to specialize, or to die and be shed. Growing in an uncontrollable manner and unable to recognize its own natural boundary, the cancer cells may spread to areas of the body where they do not belong. Cancer cells have defects in normal cellular functions that allow them to divide, invade the surrounding tissue, and spread by way of vascular and/or lymphatic systems. Characteristics of Cancer Abnormality Uncontrollability Invasiveness A Group of Diseases Unit 5.2: Cancer TermsCancer, Neoplasia, Tumor, Neoplasm The word cancer comes from the Latin (originally Greek) derived term for crab, because of the way a cancer adheres to any part that it seizes upon in an obstinate manner like the crab. Hippocrates first described cancer as having a central body with the tendency to reach out and spread like, "the arms of a crab." Besides the popular, generic term "cancer" used by most people, there is another more technical term: neoplasia. Neoplasia (neo = new, plasia = tissue or cells) or neoplasm literally means new tissue in Greek. This term indicates that cancers are actually new growths of cells in the body. Another term for cancer is "malignant tumor." Tumor literally means "swelling" or "mass." In this case, it refers to a mass of non-structured new cells, which have no known purpose in the physiological function of the body. There are two general types of tumors: benign (non-cancerous) tumors and malignant (cancerous) tumors. A benign tumor is composed of cells that will not invade other unrelated tissues or organs of the body, although it may continue to grow in size abnormally. A malignant tumor is composed of cells that resemble immature cells and invade the basement membrane or spread to other parts of the body. Malignant cells can also break away from the primary tumor and travel by blood or lymph to other body organs or by seeding or implantation in body cavities. This capability is called metastasis. Terms such as "mass" and "lump" are used to describe any overgrowth of tissue. However, these terms may not necessarily mean that such growths contain cancer cells. Types of Abnormal Cell Growth In addition to neoplasia, there are several other terms referring to abnormal cell growth. These include the following: Hyperplasia refers to an abnormal increase in the number of cells, which are in a normal component of that tissue and are arranged in a normal fashion with
subsequent enlargement of the affected part. One example is thyroid hyperplasia, an enlargement of the thyroid gland caused by an abnormal rapid growth of the epithelial cells lining the follicles. Another example is: Guitar strumming leads to hyperplasia of the cells on the thumb (a callus is formed). The callus on the thumb is a hyperplastic growth. Hyperplasia, metaplasia, and dysplasia are reversible because they are results of a stimulus. Neoplasia is irreversible because it is autonomous. Tumor Terminology Generalizations Names of benign tumors usually end with "oma" as suffixes regardless of their cell type. For example, a benign glandular tumor (epithelium tissue) is called adenoma and a benign bone tumor is called osteoma while a malignant glandular tumor is called adenocarcinoma and a malignant bone tumor is called osteosarcoma. In addition to benign tumors, there are in situ tumors and invasive tumors. In situ tumors do not invade the basement membrane, whereas invasive tumors do invade the basement membrane. Unit 5.3: Risk FactorsRisk Factors Smoking The health risks with cigarette smoking are not limited to smokers. Exposure to environmental tobacco smoke significantly increases a nonsmoker's risk of developing lung cancer. Environmental tobacco smoke is the smoke that nonsmokers are exposed to when they share air space with someone who is smoking. Diet Genetics Occupation and Environment The common body surfaces that are exposed to carcinogens are the skin, nasal passages, and lung. The primary internal body surface that has contact with carcinogens is the urinary bladder Infectious Agents Cancer risk factors are not limited to those listed above. There are still other risk factors such as ethanol use, use of certain medications, hormones, and reproductive and sexual behavior. With further scientific research, more cancer risk factors will be identified in the future. Unit 5.4: Cancer ClassificationCancers are classified in two ways: by the type of tissue in which the cancer originates, also known as the cancer’s histological type, and by the primary site, also known as the location in the body where the cancer first developed. This unit introduces you to the first method: cancer classification based on histological type. The international standard for the classification and nomenclature of histologies is the International Classification of Diseases for Oncology, Third Edition (ICD-O-3). From a histological standpoint there are hundreds of different cancers, which are grouped into five major categories: carcinoma, sarcoma, myeloma, leukemia, and lymphoma. In addition, there are also some cancers of mixed types. Carcinoma Epithelial tissue is found throughout the body. It is present in the skin, as well as the covering and lining of organs and internal passageways, such as the gastrointestinal tract. Carcinomas are divided into two major subtypes: adenocarcinoma, which develops in an organ or gland, and squamous cell carcinoma, which originates in the squamous epithelium. Adenocarcinoma generally occurs in mucus membranes and is first seen as a thickened plaque-like white mucosa. They often spread easily through the soft tissue where they occur. Squamous cell carcinoma occurs in many areas of the body. Most carcinomas affect organs or glands capable of secretion, such as the breasts, which produce milk, or the lungs, which secrete mucus, or colon or prostate or bladder. Sarcoma Examples of sarcomas are:
Myeloma Leukemia
Lymphoma Mixed Types
Cancer Types by Site Compared to those based on histological type, cancers named after the primary site may not be as accurate. For example lung cancer; the name does not specify the type of tissue involved. It simply indicates where the cancer is located. In fact, depending on how the cells look under a microscope, there are two major types of lung cancer: non-small cell lung cancer and small cell lung cancer. Non-small cell lung cancer can be further divided into various types named for the type of cells in which the cancer develops, typically: squamous cell carcinoma, adenocarcinoma, and large cell carcinoma. Small cell lung cancer, sometimes called oat cell carcinoma, is the less common form of lung cancer, making up 20% of cases. There are three types of small cell lung cancer named for the kinds of cells found in the cancer and how the cells look when viewed under a microscope. These include small cell, mixed small cell/large cell and combined small cell. Cancers are named according to the organ in which they originate. Even if a cancer metastasizes to another part of the body, it keeps its original name. Cancer names such as breast cancer, brain cancer, lung cancer, skin cancers are examples. Module 5 Review and QuizThe American Cancer Society defines cancer as "a group of diseases characterized by uncontrolled growth and spread of abnormal cells. If the spread is not controlled, it can result in death." Cancer does not refer to a single disease. Rather, it consists of more than 100 different diseases. A few cancer related terms are introduced: cancer, neoplasia, tumor, neoplasm, and growth. Neoplasia, a synonym of cancer, is often used by medical professionals. Neoplasm is a synonym for tumor, which literally means "new growth." Several other terms referring to abnormal cell growth which are not cancer include: hyperplasia, metaplasia, and dysplasia. Although scientists have not yet pinpointed an exact cause for cancer, many factors have been identified that are likely to cause development of cancer in the body. These factors are called "cancer risk factors" and include smoking, diet, genetics, occupation, environment, and infectious agents. Cancers can be classified based either on histological type or their primary site (the location where the cancer originated). Five major categories of cancer, based on their histological characteristics, are: carcinoma; sarcoma; myeloma; leukemia; and lymphoma. In addition, there are also some mixed types. The most common sites in which cancer develops include skin, lung, female breast, prostate, and colon, rectum, and corpus uteri. Quiz for Module 5 Click here to take the Module 5 Quiz. What term refers to new growth or tumors?Listen to pronunciation. (NEE-oh-PLA-zum) An abnormal mass of tissue that forms when cells grow and divide more than they should or do not die when they should. Neoplasms may be benign (not cancer) or malignant (cancer).
What is the term for the enlargement of a tissue or organ due to an increase in cell number?December 2021) Hyperplasia (from ancient Greek ὑπέρ huper 'over' + πλάσις plasis 'formation'), or hypergenesis, is an enlargement of an organ or tissue caused by an increase in the amount of organic tissue that results from cell proliferation.
Which term means enlargement of an organ or tissue abnormal increase in the number of cells not in size of cells?Before cancer cells form in tissues of the body, the cells go through abnormal changes called hyperplasia and dysplasia. In hyperplasia, there is an increase in the number of cells in an organ or tissue that appear normal under a microscope. In dysplasia, the cells look abnormal under a microscope but are not cancer.
What is hyperplasia and metaplasia?Metaplasia is the transformation of a normal tissue into another normal tissue with different structure and functions. Hyperplasia is characterized by an increased number of cells but without modification of tissue organization. Neoplasia is a tissue neoformation linked to an excessive cell proliferation.
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