Here is a compilation of essays on ‘Cancer: A Deadly Disease’ for class 8, 9, 10, 11 and 12. Find paragraphs, long and short essays on ‘Cancer: A Deadly Disease’ especially written for school and college students.
Contents
Essay on Cancer
Essay Contents:
- Essay on the Introduction to Cancer
- Essay on the Meaning of Cancer
- Essay on the Causes of Cancer
- Essay on the Incidence of Cancer
- Essay on the Mortality of Cancer
- Essay on the Classification of Cancer
- Essay on the Types of New Tissue Growth that Causes Cancer
- Essay on the Genetics of Cancer
- Essay on the Biochemical Effects of Cancer
- Essay on Benign and Malignant Tumors Causing Cancer
- Essay on the Signs and Symptoms of Cancer
- Essay on the Prevention of Cancer
Essay # 1. Introduction to Cancer:
It is difficult to imagine anyone who has not heard of the disease we call “cancer”. Ten million new cases are diagnosed annually worldwide, and the number is expected to increase to 20 million by the year 2020. If such trends continue, close to one out of every two people in the United States will eventually develop some form of the disease and cancer will be the most common cause of death.
To put it another way, in a country of roughly 300 million people we are expecting more than 100 million new cancer cases! In the face of such numbers, it is not surprising that there is widespread interest in (and fear of) the topic of cancer biology.
The good news is that enormous progress has been made in the past few decades in unravelling the cellular and molecular mechanisms that underlie the development of cancer. The study of cancer biology, once restricted almost entirely to the medical school curriculum, is becoming a topic of broad relevance to biologists as they uncover the roles of various genes and their protein products in the abnormal behavior of cancer cells.
As it turns out, investigating the properties of cancer cells has deepened our understanding of normal cells and, conversely, our rapidly expanding knowledge about the behavior of normal cells is providing numerous insights into the properties of cancer cells.
It is reasonable to expect that our growing understanding of the principles that govern the behavior of cancer cells will eventually lead to better approaches for cancer diagnosis, treatment, and prevention.
Essay # 2. Meaning of Cancer:
The meaning of the word cancer is based on differences in the growth patterns of tumors that allow them to be subdivided into two fundamentally different categories. One group consists of benign tumors, which grow in a confined local area.
In contrast, malignant tumors can invade surrounding tissues, enter the bloodstream, and spread to distant parts of the body by a process called metastasis. The term cancer is a generic term that refers to any malignant tumor—that is, any tumor capable of spreading by invasion and metastasis.
Cancer is disease in which there is uncontrolled cell growth (growth and division beyond the normal limits), invasion (intrusion on and destruction of adjacent tissues), and sometimes metastasis (spread to other locations in the body via lymph or blood). Medical term for cancer is malignant neoplasm.
Cancer is a disease in which abnormal cells proliferate in an uncontrolled fashion and spread through the body. Such cells can arise in a variety of tissues and organs, and each of these sites contains different cell types that may be affected. The net result is more than 100 kinds of cancer distinguished from one another on the basis of where they originate and the cell type involved.
Cancer is fundamentally a disease of defects in the cell’s regulatory mechanisms. In multicellular organisms, the regulation of proliferation, differentiation and survival of individual cells are carefully regulated.
Essay # 3. Causes of Cancer:
The common cause in all cancers is the acquisition of abnormalities in the genetic material of the cancer cell and its progeny. A substance causing abnormality in the cell leading to cancer is known as carcinogen.
i. Mutagens:
Substances that cause DNA mutations are known as mutagens. All mutagens do not cause cancers and mutagens that cause cancers are known as carcinogens. Tobacco smoking is associated with lung cancer and bladder cancer. Prolonged exposure to asbestos fibers is associated with mesothelioma.
ii. Chemicals:
Alcohol is a chemical carcinogen that promotes cancers through their stimulating effect on the rate of cell mitosis. Faster rates of mitosis leaves less time for repair enzymes to repair damaged DNA during DNA replication, increasing the likelihood of a genetic mistake. A mistake made during mitosis can lead to the daughter cells receiving the wrong number of chromosomes.
iii. Ionizing Radiation:
Sources of ionizing radiation, such as radon gas, can cause cancer. Prolonged exposure to ultraviolet radiation from the sun can lead to melanoma and other skin malignancies.
iv. Infectious Diseases:
Many cancers originate from a viral infection. The main viruses associated with human cancers are human papilloma virus, hepatitis B and hepatitis C virus, Epstein-Barr virus, and human T-lymphotropic virus. The mode of virally-induced tumors can be divided into two, acutely-transforming or slowly-transforming.
In acutely transforming viruses, the viral particles carry a gene that encodes for an overactive oncogene called viral-oncogene (v-onc), and the infected cell is transformed as soon as v-onc is expressed. In contrast, in slowly-transforming viruses, the virus genome is inserted, especially as viral genome insertion is an obligatory part of retroviruses, near a proto-oncogene in the host genome.
The viral promoter or other transcription regulation elements in turn cause overexpression of that proto-oncogene, which in turn induces uncontrolled cellular proliferation. Because viral genome insertion is not specific to proto-oncogenes and the chance of insertion near that proto-oncogene is low, slowly-transforming viruses have very long tumor latency compared to acutely-transforming viruses, which already carry the viral oncogene. In addition to viruses, bacteria can also cause cancer for example the chronic infection of the wall of the stomach with Helicobacter pylori causes gastric cancer.
v. Hormonal Imbalances:
Some hormones can act in a similar manner to non-mutagenic carcinogens in that they may stimulate excessive cell growth. A well-established example is the role of hyper estrogenic states in promoting endometrial cancer.
vi. Immune System Dysfunction:
HIV is associated with a number of malignancies, including Kaposi’s sarcoma, non-Hodgkin’s lymphoma, and HPV-associated malignancies such as anal cancer and cervical cancer. Certain other immune deficiency states ex. common variable immunodeficiency and IgA deficiency are also associated with increased risk of malignancy.
vii. Heredity:
A number of cancers are caused due to hereditary causes wherein there is a defective tumor suppressor allele. The examples are breast cancer and ovarian cancer which are due to inherited mutations in the genes BRCA1 and BRCA2.
viii. Other Causes:
Individuals develop cancer from tumors hiding inside organ transplants.
Essay # 4. Incidence of Cancer:
The term cancer, which means “crab” in Latin, was coined by Hippocrates in the fifth century BC to describe a family of diseases in which tissues grow and spread unrestrained throughout the body, eventually choking off life.
Although the disease has therefore existed for at least several thousand years, its prevalence has been steadily increasing. In just the past 50 years, a person’s chance of developing cancer within his or her lifetime has doubled, and doctors are now seeing more cases of the disease than ever before.
This increase has fostered the common misconception that the growing contamination of our environment by cancer-causing agents is creating a cancer epidemic. In fact, most of the increase in cancer rates has a somewhat different explanation; Cancer strikes older people more frequently than younger people, and more cancer cases are being seen simply because people are living longer than they did in the past.
The increase in average lifespan, due mainly to the availability of vaccines and antibiotics that have lowered death rates from infectious diseases, means that more and more people are living long enough to develop cancer.
Essay # 5. Mortality of Cancer:
The various kinds of cancer differ significantly in terms of how frequently they arise (Figure 1, left). The most common type is skin cancer, which accounts for roughly half of all human cancers. The next group in terms of frequency in the United States includes cancers of the prostate, breast, lung, and colon (the latter is often combined with cancer of the rectum and designated colorectal cancer).
Each of these four cancer types accounts for about 5% to 10% of all cancers. Of the dozens of other kinds of cancer routinely encountered, none accounts for more than a few percent of the total number of cancer cases.
Patterns of cancer incidence exhibit many similarities around the world, although some striking geographical differences have also been noted. When cancer rates are compared between different countries, it is crucial that the data be adjusted for two variables.
First, the countries being compared will not have the same exact number of people, so cancer rates are generally expressed per 100,000 individuals to adjust for differences in population size. Second, statistics must also be adjusted for differences in age distribution because of the higher cancer rates observed in older individuals. As a consequence, cancer rates are usually expressed as age-adjusted incidence per 100,000 people per year.
When this type of statistic is used to compare cancer rates in different countries, a number of interesting patterns emerge. The incidence rates for most cancers tend to be similar in the United States, Canada, and Western Europe, but significant differences become apparent when comparisons are made with other regions of the world.
For example, liver cancer is especially prominent in Africa and Southeast Asia, reaching age-adjusted rates in some regions of China and Thailand that are more than 25 times higher than in the United States. Likewise, stomach cancer is roughly 10 times more frequent in Japan than in the United States.
Conversely, prostate cancer is 10 times more frequent in the United States than in Japan and 20 to 40 times more frequent than in northern Africa. Colon breast and lung cancers are also especially frequent in the United States.
i. Lung Cancer Causes the most Cancer Deaths:
More than 500,000 people currently die from cancer in the United States each year, making it second only to heart disease as a cause of death. Although this statistic means that anyone who develops cancer is likely to react with feelings of fear and anxiety, it is important to understand that all forms of cancer are not equally dangerous. Most forms of skin cancer, for example, are easily cured and skin cancer is not a major source of cancer deaths, even though it is the most common type of cancer.
The number one cancer killer is not skin cancer but lung cancer, a disease that accounts for roughly one of every three cancer deaths in the United States (see Figure 1, right). Lung cancer is one of the five most frequent types of cancer, and it also has the worst prognosis of the five, killing roughly 85% of affected individuals within five years of diagnosis.
Colorectal, breast, and prostate cancers are also among the top five in terms of total cancer fatalities, although their survival rates are significantly better than is seen with lung cancer. Cancer of the pancreas, which does not even fall among the top ten cancers in terms of overall frequency, is the fourth leading cause of cancer deaths in the United States because it is one of the most difficult cancers to treat successfully, killing an even higher percentage of its victims than does lung cancer.
ii. The Prevalence of Various Cancers has Changed over Time:
Although lung cancer is currently the number one cancer killer in the United States that has not always been the case. Lung cancer was one of the rarest forms of cancer 100 years ago, so rare that in a book written about lung cancer in the early 1900s, the author apologized for devoting so much time to such an esoteric subject! The past century, however, has seen a steady and dramatic increase in lung cancer rates, to the point where an obscure disease has been transformed into a major public health problem.
Recall that when we assess long-term cancer trends, the data need to be adjusted for age; otherwise, all forms of cancer will appear to be increasing in frequency because people are living longer and cancer is largely a disease of the elderly. Figure 2 provides age-adjusted data showing the long-term trends in cancer rates for several types of cancer.
The data reveal that even when the statistics are adjusted for age, a dramatic increase in lung cancer rates has occurred since 1930. Yet most kinds of cancer (such as colorectal and breast cancer shown in Figure 2) have not changed much in age-adjusted incidence, and a few kinds of cancer are even decreasing in frequency.
Stomach cancer is a particularly striking example. Since 1930, the annual death rate from stomach cancer has dropped about fivefold in the United States. While an astute observer might question whether such data reflect an improvement in cancer treatment rather than a decrease in stomach cancer rates, this explanation does not hold; survival rates for stomach cancer have improved only slightly, and the disease still kills about 80% of its victims within five years of diagnosis.
The discovery that stomach cancer rates were decreasing at the same time that lung cancer rates were increasing makes it fairly clear that different kinds of cancer have different causes. The increase in lung cancer rates is attributed to the fact that lung cancer is caused by smoking cigarettes, a practice that became increasingly popular during the twentieth century.
The reason for the decrease in stomach cancer rates is not as well understood, but it is thought to be related to changes in diet and the growing use of antibiotics, which kill the bacteria involved in triggering stomach cancer. In Japan, where the traditional diet is quite unlike that in the United States, stomach cancer rates are almost ten times higher and stomach cancer kills almost as many Japanese as does lung cancer.
Essay # 6. Classification of Cancer:
Cancer markers can be classified in two groups: cancer-specific markers and tissue- specific markers:
i. Cancer-Specific Markers:
Cancer-specific markers are related to the presence of certain cancerous tissue. Because there is a large overlapping between the many different tumor tissue types and the markers produced by these cancer tissues might not be specific in making a diagnosis. They can however, be useful in the follow-up of treated patients to describe progress of the disease or response to treatment. A few examples of these markers are CEA, CA19-9, CA125.
An example of a cancer-specific marker, CEA, or carcinoembryonic antigen, is a blood-borne protein, first noted to be produced by tumors of the gastrointestinal system. Further investigation showed that it was produced by the occasional lung and breast cancer case, meaning that an elevated level does not mean a bowel cancer.
However, in a patient with a history of a treated bowel cancer, a rising CEA level can be an early sign of bowel cancer return. This usually occurs before the site of return can be identified on imaging or examination and so many oncologists question the wisdom of doing a blood test for CEA when the end result is bad news that alarms the patient.
Nevertheless, a sequence of steady low CEA readings can provide much needed reassurance to the post-operative patient. Also, a rising sequence of CEA readings should alert the physician to the need for diagnostic tests such as PET scans.
ii. Tissue-Specific Markers:
Tissue-specific markers are related to specific tissues which have developed cancer. Generally, these substances are not specifically related to the tumor, and may be present at elevated levels when no cancer is present. But unlike the previous group, elevated levels point to a specific tissue being at fault.
Examples include PSA, beta-HCG—(human chorionic gonadotropin), AFP—(alpha-fetoprotein), AFP-L3—(a lectin-reactive AFP) and thyroglobulin. For example, if man has an elevated PSA, a search for prostate cancer will be undertaken. If an individual has an elevated level of beta-HCG, AFP or AFP-L3%, a search for a testicular or liver cancer respectively, will be made.
PSA (Prostate Specific Antigen):
Is produced by the normal prostate. It is a protein enzyme called a serine protease that usually acts as an anticoagulant to keep semen liquid. Only small amounts leak into the circulation in normal circumstances. Enlarged prostates leak more substantial amounts, and cancerous prostates also leak substantial amounts.
β-hCG:
Elevated levels cannot prove the presence of a tumor, and low levels do not rule it out (an exception is in males who do not naturally produce β-hCG). Nevertheless, elevated βhCG levels fall after successful treatment (e.g. surgical intervention or chemotherapy), and a recurrence can often be detected by the finding of rising levels.
Essay # 7. Types of New Tissue Growth that Causes Cancer:
i. Hypertrophy and Hyperplasia Involve an Increase in the Size or Number of Normal Cells:
In many situations, new tissue growth occurs as part of a normal physiological response to a particular stimulus. For example, if you were to start a new job that involves lifting heavy objects, your muscles would soon grow larger in response to the physical activity.
Professional athletes and body builders adapt this principle when they use weight-lifting exercises to build muscle mass, yet the growing muscles on their arms and legs are not signs of cancer! Or perhaps you want to learn how to play the guitar.
You will find that after a few days of practice, the skin on the tips of your fingers becomes thickened with calluses from pressing on the strings. Once again, the growing calluses on your fingertips are not signs of cancer.
The preceding examples illustrate two types of new tissue growth, neither of which is cancer. The increase in muscle mass triggered by exercise arises from the growth of individual muscle cells rather than an increase in the number of muscle cells. Such tissue growth based on an increase in cell size is called hypertrophy (Figure 3a).
In contrast, calluses are produced by hyperplasia, a process in which cell division creates an increased number of normal cells (Figure 3b). In both cases, the process is potentially reversible. If you stop exercising or stop playing the guitar, the size of your muscles will decrease or your calluses will disappear.
ii. Dysplasia and Neoplasia are Characterized by Abnormalities in Cell Organization and Proliferation:
When a piece of tissue in which hypertrophy or hyperplasia has occurred is examined with a microscope, the cell and tissue organization will look relatively normal. In contrast, the next type of tissue growth to be considered, called dysplasia, is an abnormal growth process that produces tissue in which proper cell and tissue organization have been disrupted (Figure 3c).
The extent of the abnormalities varies across a broad range referred to as mild, moderate, or severe dysplasia. One site in which dysplasia commonly arises is the uterine cervix; the Pap smear is a routine screening procedure that can detect uterine dysplasia in its early stages before it has progressed to a more serious condition.
Dysplasia has two possible outcomes. In some cases, especially in its less severe forms, dysplasia is reversible and the tissue will revert back to normal appearance and behavior. Alternately, dysplasia can become more severe, eventually progressing to a more dangerous form of tissue growth known as Neoplasia.
Neoplasia is an abnormal type of tissue growth in which cells proliferate in an uncontrolled, relatively autonomous fashion, leading to a continual increase in the number of dividing cells (Figure 3d).
This loss of growth control creates a proliferating mass of abnormal cells called a neoplasm or tumor. Uncontrolled proliferation does not mean that tumor cells always divide more rapidly than normal cells. The crucial issue is not the rate of cell division but rather the relationship between cell division and cell differentiation, the process by which cells acquire the specialized properties that distinguish different types of cells from one another.
Cell differentiation is a trait of multicellular organisms, which are composed of complex mixtures of specialized or “differentiated” cell types. For example; nerve, muscle, bone, blood, cartilage, and fat—brought together in various combinations to form tissues and organs. The various types of differentiated cells are distinguished from one another by differences in their structural organization and in the products they manufacture.
For example, red blood cells produce hemoglobin, nerve cells synthesize chemicals that transmit nerve impulses, and pancreatic islet cells make insulin, and so forth. In addition to manufacturing such specialized products, differentiated cells often lose the capacity to divide.
In normal tissues, the rates of cell division and cell differentiation are kept in proper balance. To illustrate, let us briefly consider normal cell proliferation in the skin, where new cells are continually being produced to replace the cells being shed from the outer surfaces of the body. These replacement cells are generated through the division of undifferentiated cells located in the basal layer of the skin (Figure 4, top).
Each time one of these basal cells divides, it gives rise to two cells with differing fates. One cell stays in the basal layer and retains the capacity to divide, whereas the other cell loses the capacity to divide and undergoes differentiation as it leaves the basal layer and moves toward the outer skin surface.
As it differentiates, the migrating cell gradually acquires a flattened shape and begins to make keratin, the fibrous structural protein that imparts mechanical strength to the outer layers of the skin. The fully differentiated, thin flat cells that form the outer layer of the skin look almost like scales and are referred to as squamous cells.
Because only one of the two cells produced by each basal cell division normally retains the capacity to divide, there is no increase in the total number of dividing cells. Cell divisions are simply creating new differentiated cells to replace the ones that are being lost from the outer surface of the skin.
A similar phenomenon takes place in the bone marrow, where new blood cells are produced to replace aging blood cells that are constantly being destroyed, and in the lining of the gastrointestinal tract, where new cells are produced to replace the cells that are being shed. In each of these situations, cell division is carefully balanced with cell differentiation so that no net accumulation of dividing cells takes place.
In tumors, this finely balanced arrangement is disrupted and some cell divisions give rise to two cells that both continue to divide, thereby feeding a progressive increase in the number of dividing cells (see Figure 4, bottom right). If the cells divide quickly, the tumor will rapidly increase in size; if the cells divide more slowly, tumor growth will be slower.
But regardless of how slow or fast the cells divide, the tumor will continue to grow because new cells are being produced in greater numbers than needed. As the dividing cells accumulate, the normal organization and function of the tissue gradually become disrupted (Figure 5).
Essay # 8. Genetics of Cancer:
All living and cellular organisms grow by division of cells. The cells arise by division of a parent cell. Every young cell grow, differentiate and then die after a predetermined time. Such birth and death processes continuously occur in nature unless interrupted otherwise.
Cells grow and divide in precisely controlled manner, each step regulated by a specific gene. Due to a defective gene, cell growth spins out of control. This is cancer. In cancer, there is specific alteration in growth pattern of cells.
Cancer is a large class of diverse diseases, all of which exhibit uncontrolled cell growth and division. In non-circulatory tissues, such uncontrolled cell growth produces cell masses, called tumours (neoplasms).
Cancerous or malignant tumours are those from which cells detach and migrate through blood or lymph to other parts of the body, giving rise to secondary tumors (process called metastasis). Non-cancerous or benign tumors do not metastasise, i.e., benign tumours remain localised to a particular area.
Few essential facts about cancer:
When a normal cell becomes tumourigenic, three types of changes occur in them. They are:
1. Immortalisation:
Cells acquire the property to grow indefinitely.
2. Transformation:
Cells bypass normal control on growth which restrain other cells.
3. Metastasis:
Cells gain the ability to invade other tissues of the body.
In the mid 1970s, American microbiologists John Michael Bishop and Harold Varmus showed that oncogenes are the altered or mutated forms of normal genes, the proto-oncogenes.
Two classes of genes are found to regulate the growth of cells:
1. Proto-Oncogenes:
These genes encourage cell growth. An inappropriate activation of such genes can over-stimulate cell growth causing tumours.
2. Tumor Suppressor Genes or Anti-Oncogenes:
These genes tend to inhibit cell growth. Loss or inactivation of such genes eliminate the necessary constraints on cell growth, thereby keeping the cell constantly active.
Cancers are named according to the tissues from which they arise, usually with the suffix – ” – oma”. They are generally divided into four main groups, dependent on the types of cells originally involved. Two types of cancer cause overproduction of white blood cells.
Leukemias are diseases that cause excessive production of leucocytes, which originate in the bone marrow. Lymphomas cause excessive production of lymphocytes, which originate in the lymph nodes and spleen. Sarcomas are tumors of tissues such as muscle, bone and cartilage that arise from the embryological mesoderm.
About 85% of cancers are carcinomas, tumors arising from epithelial tissues such as glands, breast, skin and linings of the urogenital, digestive and respiratory systems.
Melanoma is a malignant tumor of the skin containing dark pigment melanin.
Human cancers are responsible for an enormous amount of suffering. A large amount of money and efforts have been directed to the study of these diseases. Although there has been great progress in the detection and treatment of cancers, there has been little progress towards understanding the molecular basis of cancer (see Gardner et al. 2001).
All cancers are genetic in nature. They originate due to alterations of genes that control cell growth. Most evidence indicates that cancers are clonal,i.e., they arise from a single aberrant cell that then proliferates.
Therefore, analysing the causes of cancer involves the understanding how one cell is changed or transformed, from a normal cell to a cancerous one. According to clonal evolution theory of cancer, most cancers come about from a series of genetic changes, progressively cancerous one.
Most evidently, cancers are caused by either mutation or viruses. Viruses are known to bring cancer causing genes (oncogenes) into cells, where their mutated forms or improper locations can lead to cancer.
Thus, both the mutational and viral views of cancer are ultimately concerned with mutation. In other words, it can be said that cancers result from those genes which were changed by mutation or were imported or activated by viruses.
Essay # 9. Biochemical Effects of Cancer:
i. The tumour cells behave like foetal cells rather than adult cells (hence fast mitosis).
a. There is re-expression of foetal antigens like α-feto-protein.
b. Synthesis of isoenzymes which are characteristic of foetal cells and lacking in adult cells. Ex. A placental type of alkaline phosphatase is found in carcinomas.
ii. Most cancers elaborate protease and glycosidases which contribute to their invasiveness as well as to, many of the alternation in surface properties.
iii. There is an increase in cellular respiration mechanism (ETC).
iv. There is an increased rate of glycolysis.
v. Some tumour inducing viruses act as ATPase hydrolyzing ATP to ADP and Pi, thereby lowering the ATP/ADP ratio leading to increased glycolysis and more production of lactic acid.
vi. The circulating levels of cAMP are decreased whereas the cAMP phosphodiesterase activity is increased.
vii. Excretion of adrenaline and nor-adrenaline increases.
viii. A number of polypeptide hormones are produced by tumour tissues.
ix. Fibro-sarcomas synthesize insulin.
x. A primary liver carcinoma produces an aldolase isoenzyme characteristics of muscle.
xi. There are abnormally high levels of the enzyme “terminal deoxynucleotidyl transferase (TDT)” in leukemia.
xii. The levels of acetylcholine, Cortisol, histamine and the metabolizing enzymes of catecholamine’s i.e. plasma dopamine -P-hydroxylase (DPH) are increased in cancers.
xiii. The levels of acetylcholine esterase and catecholamine oxidase are lowered in blood. A defective LDH4 isoenzyme is formed in WBC malignancies.
xiv. Bence Jones proteins are excreted in urine during multiple myeloma.
xv. There is a remarkable increase in urinary polyamines. They are essential growth factors for human liver. Polyamines interact with nucleic acids and enhance the DNA, RNA and protein synthesis.
xvi. Cancer cells produce excessive mucins (membrane surface glycoproteins), which mask surface antigens on cells and protect the cells from immune surveillance.
xvii. They produce abnormal cell surface glycoproteins which leads to their separation from their parent tissue and migrate to another part of the body (metastasis).
Essay # 10. Benign and Malignant Tumors Causing Cancer:
Table 1 summarizes some of the properties of benign and malignant tumors. One distinguishing feature is that malignant tumors are frequently life threatening, whereas benign tumors usually are not. The reason for the difference is that the cells of a malignant tumor have often spread to other parts of the body by the time a person is diagnosed as having cancer.
A surgeon will frequently be able to remove the original tumor, but cancer cells that have already spread through the body are difficult to locate and treat. Malignant tumors therefore tend to be more hazardous than benign ones, although some exceptions do occur.
For example, the most common forms of skin cancer rarely metastasize and are easy to diagnose and remove, so these skin cancers are hardly ever fatal. Certain benign tumors, on the other hand, arise in surgically inaccessible locations, such as the brain, making them hazardous and potentially life threatening.
Differences in growth rate and state of differentiation are also common between benign and malignant tumors. Benign tumors generally grow rather slowly and are composed of well-differentiated cells, meaning that the cells bear a close structural and functional resemblance to the normal cells of the tissue in which the tumor has arisen.
Malignant tumors, on the other hand, often (but not always) grow more rapidly and their state of differentiation is variable, ranging from relatively well-differentiated tumors to tumors whose cells are so poorly differentiated that they bear almost no resemblance to the original cells from which they were derived.
Benign and Malignant Tumors (Cancer) are Named using a Few Simple Rules:
Because tumors can arise from a variety of cell types located in different tissues and organs, some basic conventions have been established to facilitate the naming of tumors.
Depending on their site of origin, cancers are grouped into three main categories:
(1) Carcinomas are cancers that arise from the epithelial cells that form covering layers over external and internal body surfaces. Carcinomas are by far the most common type of malignant tumor, accounting for roughly 90% of all human cancers.
(2) Sarcomas are cancers that originate in supporting tissues such as bone, cartilage, blood vessels, fat, fibrous tissue, and muscle. They are the rarest group of human cancers, accounting for about 1% of the total.
(3) The remaining cancers are the lymphomas and leukemias, which arise from cells of lymphatic and blood origin. The term lymphoma refers to tumors of lymphocytes (white blood cells) that grow mainly as solid masses of tissue, whereas leukemias are cancers in which malignant blood cells proliferate mainly in the bloodstream.
Within each of the three groups, individual cancers are named using prefixes that identify the cell type involved. For example, consider a cancer arising from a gland cell, which is a specialized type of epithelial cell. Such a cancer is named by inserting the prefix adeno- (meaning “gland”) in front of carcinoma (the term for epithelial cancers), yielding the name adenocarcinoma.
Depending on the organ where it originated, the tumor might be called a lung adenocarcinoma, a colon adenocarcinoma, a breast adenocarcinoma, and so forth. What if the tumor were benign instead of malignant? In this case the suffix -oma is used instead of -carcinoma, yielding the name adenoma. Cancers of supporting tissue origin are named in a similar fashion, except the suffix -sarcoma is employed instead of -carcinoma. Thus a cancer of bone cells is called an osteosarcoma (the prefix osteo- means “bone”), and a benign tumor of bone is an osteoma.
Once you know the meanings of the prefixes that designate each of the common cell types, it is relatively straightforward to construct the proper technical names for a wide variety of tumors. The meanings of these prefixes, and the ways in which they are combined to create tumor names, are summarized in Table 2.
Malignant tumors can usually be recognized by the presence of “carcinoma” or “sarcoma” in their name, but there are several exceptions. For example, despite their benign-sounding names, melanomas are malignant tumors of pigmented cells, lymphomas are malignant tumors of lymphocytes, and myelomas are malignant tumors of bone marrow cells.
The tumor names listed in Table 2 refer to the site at which a tumor initially arises the so-called primary tumor. For example, a tumor discovered in a person’s liver might be a liver adenocarcinoma, but it might also consist of stomach or colon cancer cells that had metastasized to the liver via the bloodstream and began growing there. In such cases, the tumor is not a liver cancer but rather a colon or stomach cancer that has metastasized to the liver.
Essay # 11. Signs and Symptoms of Cancer:
Signs and symptoms of cancer as follows:
i. Unusual lumps or swelling (tumor),
ii. Hemorrhage (bleeding),
iii. Pain and/or ulceration,
iv. Enlarged lymph nodes,
v. Cough,
vi. Hemoptysis,
vii. Hepatomegaly (enlarged liver),
viii. Bone pain,
ix. Fracture of affected bones and neurological symptoms,
x. Weight loss,
xi. Poor appetite,
xii. Fatigue and cachexia (wasting),
xiii. Excessive sweating (night sweats),
xiv. Anemia and specific Para neoplastic phenomena, i.e. specific conditions that are due to an active cancer, such as thrombosis or hormonal changes.
Diagnosis:
People with suspected cancer are investigated with medical tests. These commonly include blood tests, X-rays, CT scans and endoscopy.
Treatment:
Cancer can be treated by surgery, chemotherapy, radiation therapy, immunotherapy, monoclonal antibody therapy or other methods.
Tumor marker:
A tumor marker is a substance found in the blood, urine, or body tissues that can be elevated in cancer, among other tissue types. There are many different tumor markers, each indicative of a particular disease process, and they are used in oncology to help detect the presence of cancer. An elevated level of a tumor marker can indicate cancer; however, there can also be other causes of the elevation.
Description:
Tumor markers can be produced directly by the tumor or by non-tumor cells as a response to the presence of a tumor.
They can be identified by:
i. Screening for common cancers on a population basis, ex. elevated prostate specific antigen suggests prostate cancer.
ii. Monitoring of cancer survivors after treatment, ex. elevated AFP in a child previously treated for teratoma suggests relapse with endodermal sinus tumor.
iii. Diagnosis of specific tumor types, particularly in certain brain tumors and other instances where biopsy is not feasible.
iv. The term tumor antigen is sometimes interchangeably used for tumor marker.
Essay # 12. Prevention of Cancer:
Cancer research is motivated to a large extent by the belief that a better understanding of the disease will lead to better approaches for treatment and prevention. For example, our increasing knowledge of the role played by specific genes and proteins in cancer development has prompted a variety of new treatment strategies. Likewise, knowing the causes of cancer provides crucial information as to how cancer can be prevented, and as the old saying goes, “An ounce of prevention is worth a pound of cure.”
One approach for preventing cancer is based on the discovery that many types of cancer are caused by known environmental agents and behaviors; avoiding these causes of cancer will therefore decrease a person’s risk of developing the disease.
A second approach for preventing cancer is based on the realization that cancers arise through a multistep process that usually unfolds over a period of several decades rather than occurring as a single discrete event.
So even if a person has already been exposed to agents that “cause” cancer, there are opportunities to intervene and block one of the subsequent steps required for the progression to malignancy.
Current statistics suggest that if people adopt both prevention approaches—that is, reduce their exposure to cancer-causing agents and take steps that help protect against cancer development after such agents have been encountered—more than half of all cancer deaths could be prevented.