Cancer registry part 3

Categories of Cancer

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 cancer are examples. However, cancer names may also be based on the type of tissue affected. This section will introduce you to some basics regarding the derivation of tissues in the context of embryology, which is the study of the development of an organism.

Derivation of Cells

Human beings begin life as a single, newly fertilized cell. Like every cell that contains a nucleus, the fertilized cell holds all the instructions for its growth and development. The characteristics common to all living cells include the ability to reproduce, exchange gases, move, react to external stimuli, and create or utilize energy to perform their tasks.

Shortly after the ovum or egg is fertilized, it divides to form two cells. These two cells then divide to form a total of four, which again divide to form eight and continues on. This group of cells continues dividing; after nine days it attaches to the wall of the uterus and becomes an embryo.

About two weeks after conception, the cells of the embryo continue to divide, changing their shape and structure. This process is known as differentiation. The cells arrange into distinct layers called germ layers: an outer ectoderm and inner endoderm (entoderm). A third embryonic layer, the mesoderm, develops between the ectoderm and the endoderm. All the organs of the body develop or differentiate in an orderly fashion from these three primary germ layers.

Derivation of Tissues

Cells that are similar in structure tend to group themselves together and form tissues. A tissue, then, is composed of a group of cells that are similar in structure and perform one or more common functions. Some tissues contain intercellular material which is very important in the performance of a particular function belonging to that tissue.

The body tissues and organs develop from the three primary germ layers that form during the growth process of the human embryo.

The tissues derived from the ectoderm are: some epithelial tissue (epidermis or outer layer of the skin, the lining for all hollow organs which have cavities open to a surface covered by epidermis), modified epidermal tissue (fingernails and toenails, hair, glands of the skin), all nerve tissue, salivary glands, and mucous glands of the nose and mouth.

In fact, epithelial tissue can be derived from either the ectoderm or endoderm. The epithelial tissue derived from the endoderm includes the epithelial lining of the digestive tract, except at the open ends, and the epithelial lining of all hollow structures formed as outpockets in the digestive tract. This includes:

• The parenchyma of the liver including communicating or connecting ducts
• The lining of the pharynx and respiratory tract (except the nose). This includes the lungs and the passageways leading from the pharynx to the lungs
• The epithelium of the bladder and urethra
• Glands that form secretions in the digestive tract

Epithelial tissue derived from ectoderm is generally squamous epithelium; epithelial tissue derived from endoderm is essentially glandular epithelium.

There are a variety of body tissues derived from the third or middle primary germ layer known as the mesoderm. These body tissues include:

• Muscles
• Fibrous tissue
• Bone and cartilage
• Fat or adipose tissue
• Blood and lymph vessels
• Blood cells

In the early embryo the first cavity that develops is the coelomic cavity; this is derived from mesoderm. Parts of the urinary and genital systems are derived as outpouchings of the coelomic cavity. Later this coelomic cavity divides into the pleural cavity and the pericardial cavity. The linings of these cavities are composed of a single layer of cells called mesothelium. A few epithelial cells are of mesodermal origin, e.g. endometrium of the uterus, vaginal epithelium, and mucosa of the bladder.

Endothelium derived from mesoderm lines the blood and lymphatic vessels and the walls of the heart. In the capillaries where the endothelium is covered only by a basement membrane, diffusion takes place. It is surrounded elsewhere by supportive layers of connective tissue and smooth muscle. This is necessary because the endothelium is so thin that diffusion would occur otherwise. Many authorities classify this endothelium as connective tissue.

Cancer Classification

Cancers are classified in two ways: by the type of tissue in which the cancer originates (histological type) and by primary site, or the location in the body where the cancer first developed. This section 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 six major categories:

• Carcinoma
• Sarcoma
• Myeloma
• Leukemia
• Lymphoma
• Mixed Types

Carcinoma

Carcinoma refers to a malignant neoplasm of epithelial origin or cancer of the internal or external lining of the body. Carcinomas, malignancies of epithelial tissue, account for 80 to 90 percent of all cancer cases.

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.

Adenocarcinomas generally occur in mucus membranes and are first seen as a thickened plaque-like white mucosa. They often spread easily through the soft tissue where they occur. Squamous cell carcinomas occur 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

Sarcoma refers to cancer that originates in supportive and connective tissues such as bones, tendons, cartilage, muscle, and fat. Generally occurring in young adults, the most common sarcoma often develops as a painful mass on the bone. Sarcoma tumors usually resemble the tissue in which they grow.

Examples of sarcomas are:

• Osteosarcoma or osteogenic sarcoma (bone)
• Chondrosarcoma (cartilage)
• Leiomyosarcoma (smooth muscle)
• Rhabdomyosarcoma (skeletal muscle)
• Mesothelial sarcoma or mesothelioma (membranous lining of body cavities)
• Fibrosarcoma (fibrous tissue)
• Angiosarcoma or hemangioendothelioma (blood vessels)
• Liposarcoma (adipose tissue)
• Glioma or astrocytoma (neurogenic connective tissue found in the brain)
• Myxosarcoma (primitive embryonic connective tissue)
• Mesenchymous or mixed mesodermal tumor (mixed connective tissue types)

Myeloma

Myeloma is cancer that originates in the plasma cells of bone marrow. The plasma cells produce some of the proteins found in blood.

Leukemia

Leukemias ("liquid cancers" or "blood cancers") are cancers of the bone marrow (the site of blood cell production). The word leukemia means "white blood" in Greek. The disease is often associated with the overproduction of immature white blood cells. These immature white blood cells do not perform as well as they should, therefore the patient is often prone to infection. Leukemia also affects red blood cells and can cause poor blood clotting and fatigue due to anemia. Examples of leukemia include:

• Myelogenous or granulocytic leukemia (malignancy of the myeloid and granulocytic white blood cell series)
• Lymphatic, lymphocytic, or lymphoblastic leukemia (malignancy of the lymphoid and lymphocytic blood cell series)
• Polycythemia vera or erythremia (malignancy of various blood cell products, but with red cells predominating)

Lymphoma

Lymphomas develop in the glands or nodes of the lymphatic system, a network of vessels, nodes, and organs (specifically the spleen, tonsils, and thymus) that purify bodily fluids and produce infection-fighting white blood cells, or lymphocytes. Unlike the leukemias which are sometimes called "liquid cancers," lymphomas are "solid cancers." Lymphomas may also occur in specific organs such as the stomach, breast or brain. These lymphomas are referred to as extranodal lymphomas. The lymphomas are subclassified into two categories: Hodgkin lymphoma and Non-Hodgkin lymphoma. The presence of Reed-Sternberg cells in Hodgkin lymphoma diagnostically distinguishes Hodgkin lymphoma from Non-Hodgkin lymphoma.

Mixed Types

The type components may be within one category or from different categories. Some examples are:

• adenosquamous carcinoma
• mixed mesodermal tumor
• carcinosarcoma
• teratocarcinoma

  Tumor List

  Different body tissue types give rise to different tumors, both benign and malignant. The following tables show the different kinds of tumors each of the following tissue types are vulnerable to:
  • Connective Tissue
  • Endothelium and Mesothelium
  • Blood and Lymphoid Cells
  • Muscle
  • Epithelial Tissues
  • Neural
  • APUD System (APUD - Amine Precursor Uptake and Decarboxylation)
  • Other Neural Crest-Derived Cells
  • Tumors
  • Gonadal Tumors

  Connective Tissue

  Tissue	Benign Tumors	Malignant Tumors
  Adult fibrous tissue	Fibroma	Fibrosarcoma
  Embryonic (myxomatous) fibrous tissue	Myxoma	Myxosarcoma
  Fat	Lipoma	Liposarcoma
  Cartilage	Chondroma	Chondrosarcoma
  Bone	Osteoma	Osteosarcoma
  Notochord	—	Chordoma
  Connective tissue, probably fibrous	Fibrous histiocytoma	Malignant fibrous histiocytoma

  Endothelium and Mesothelium

  Tissue	Benign Tumors	Malignant Tumors
  Blood vessels	Hemangioma, hemangiopericytoma	Hemangiosarcoma, angiosarcoma
  Lymph vessels	Lymphangioma	Lymphangiosarcoma
  Mesothelium	—	Mesothelioma

  Blood and Lymphoid Cells

  Tissue	Benign Tumors	Malignant Tumors
  Hematopoietic cells	"Preleukemias", "myeloproliferative disorders"	Leukemia, of various types; aleukemic leukemia
  Lymphoid tissue	Plasmacytosis	Plasmacytoma; multiple myeloma; Hodgkin lymphoma and Non-Hodgkin lymphoma

  Muscle

  Tissue	Benign Tumors	Malignant Tumors
  Smooth muscle	Leiomyoma	Leiomyosarcoma
  Striated muscle	Rhabdomyoma	Rhabdomyosarcoma

  Epithelial Tissues

  Tissue	Benign Tumors	Malignant Tumors
  Stratified squamous	Papilloma Seborrheic keratosis and some skin adnexal tumors	Squamous cell carcinoma; epidermoid carcinoma and some malignant skin adnexal tumors
  Glandular epithelium Liver Kidney Bile duct	Adenoma Hepatic adenoma Renal tubular adenoma Bile duct adenoma	Adenocarcinoma Hepatoma: hepatocellular carcinoma Renal cell carcinoma; hypernephroma Cholangiocarcinoma
  Transitional epithelium	Transitional cell papilloma	Transitional cell carcinoma
  Placenta	Hydatidiform mole	Choriocarcinoma
  Testis	—	Seminoma; embryonal cell carcinoma

  Neural

  Tissue	Benign Tumors	Malignant Tumors
  Glial cells (of several types)	—	Glioma, grades I-III, anaplastic; glioblastoma multiforme (grade IV)
  Nerve cells	— — Ganglioneuroma	Neuroblastoma Medulloblastoma —
  Meninges	Meningioma	Malignant meningioma
  Nerve sheath	Schwannoma, neurilemmoma Neurofibroma	Malignant meningioma Malignant schwannoma Neurofibrosarcoma

  APUD System (APUD - Amine Precursor Uptake and Decarboxylation)

  The APUD system is a recently defined series of cells which have endocrine functions in that they secrete one of a variety of small amine or polypeptide hormones. The stored forms of these hormones located in the cytoplasm are small, dense-core membrane-bound granules visible by electron microscopy. Some of these cells appear to be derived from neural crest cells which migrate into a variety of organs. APUD system tissues give rise to the benign and malignant tumors outlined in Table G.

  Tissue	Benign Tumors	Malignant Tumors
  Pituitary	Basophilic adenoma Eosinophilic adenoma Chromophobe adenoma	— — —
  Parathyroid	Parathyroid adenoma	Parathyroid carcinoma
  Thyroid (C cells)	C cell hyperplasia	Medullary carcinoma of thyroid
  Bronchial lining (Kultschitzky cells)	—	Bronchial carcinooid; oat cell carcinoma
  Adrenalmedulla Pheochromocytoma	Pheochromocytoma	Malignant Pheochromocytoma
  Pancreas	Islet celladenoma; Insulinoma; gastrinoma	Islet cell carcinoma
  Stomach and intestines	Carcinoid	Malignant carcinoid
  Carotid body and chemo-receptor system	Chemodectoma; paraganglioma	Malignantcarcinoid Malignant paraganglioma

  Other Neural Crest-Derived Cells

  Tissue	Benign Tumors	Malignant Tumors
  Pigment-producing cells in skin, eyes, and occasional other sites	Nevus	Melanoma
  Schwann cells of peripheral nervous system	Schwannoma, or neurilemmoma	Malignant schwannoma
  Merkel cells in squamous epithelium (unknown function)	—	Merkel cell neoplasm (similar to oat cell)

  Tumors

  Tissue	Benign Tumors	Malignant Tumors
  Breast	Fibroadenoma	Cystosarcoma phylloides
  Renal anlage	—	Wilms tumor

  Gonadal Tumors

  Terminology for Gonadal tumors or tumors of the ovary and testis is somewhat more confusing. One general class of tumors arises from multi-potential cells that give rise to tumors containing a variety of tissue types, often within the same tumor. These "germ cell" tumors include seminoma (dysgerminoma in women), choriocarcinoma, embryonal carcinoma, endodermal sinus tumor, and teratocarcinoma. Although all of these tumors are most common in the ovaries or testes, they also occur in extragonadal sites.
  Another group of Gonadal tumors arises from the connective tissue stroma. In males, these include Sertoli-Leydig cell tumors (homologous tumors in females may be arrhenoblastoma, although most pathologists use "Sertoli-Leydig cell"), and in females, granulose-theca cell tumors, hilar cell tumors, and lipid cell tumors. Although all of these tumors technically arise from the connective tissues, they are given separate names because of the specialized nature and function of the Gonadal stromal cells.
  A number of epithelial tumors occur in the ovary. It will be easy to distinguish benign from malignant tumors because they are named in exactly the same way as other epithelial lesions. However, in some lesions, the pathologist may call a tumor "borderline" or "of low malignant potential." These terms are applied to a group of potentially malignant lesions that metastasize

• Cancer Types by Site

  Medical professionals frequently refer to cancers based on their histological type. However, the general public is more familiar with cancer names based on their primary sites. The most common sites in which cancer develops include:
  • Skin
  • Lungs
  • Female Breasts
  • Prostate
  • Colon and Rectum
  • Cervix and Uterus
  Compared with those based on histological type, cancers named after the primary site may not be as accurate. Take lung cancer for example; 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.
  However, it's important to know that cancer can be classified either by the cell type or its primary site. Saying that a woman has uterine carcinoma or uterine cancer is the same thing as saying that she has cancer (or carcinoma) of the uterus.
  Following are some examples of common types of cancers named for their primary site.

  Skin

  There are three primary types of skin cancer: basal cell, squamous cell, and melanoma. These cancers are derived from the epidermal layers with the same names. Melanomas are derived from the melanocytes, or pigment cells, in the deepest level of the epidermis.
  Basal cell and squamous cell cancers usually occur on parts of the body exposed to the sun, such as the face, ears, and extremities. These cancers are highly curable, especially if detected and treated early. Melanomas, which form dark moles that spread over the surface of the skin, are more lethal because they metastasize very quickly.

  Lung

  Lung cancer is very difficult to detect at an early stage because the symptoms often do not appear until the disease has advanced. The symptoms include persistent cough, sputum streaked with blood, chest pain, and repeated attacks of pneumonia or bronchitis.

  Female Breast

  It has been estimated that in the U.S., about 1 in 8 women will eventually develop breast cancer in her lifetime. Most breast cancers are ductal carcinomas. Women most likely to develop the disease are those over the age of 50; those who have already had cancer in one breast; those whose mother or sister had breast cancer; those who never had children; and those who had their first child after the age of 30. Other risk factors include obesity, a high-fat diet, early menarche (age menstruation begins) and late menopause (age menstruation ceases).
  Monthly breast self-examination is recommended as a way to detect breast cancer early. Most of the lumps found in the breasts are not cancerous, but women should see their physicians to find out for sure. The American Cancer Society also recommends periodic mammograms (or breast X-rays) for all women over the age of 40 as well as physical examinations of the breast by a physician for all women over the age of 20, even if they have no symptoms of breast cancer.

  Prostate

  Cancer of the prostate is found mainly in older men. As men age, the prostate may enlarge and block the urethra or bladder. This may cause difficulty in urination or interfere with sexual functions. This condition is called benign prostatic hypertrophy (BPH). Although BPH is not cancerous, surgery may be needed to correct it. The symptoms of BPH, or of other problems in the prostate, may be similar to symptoms for prostate cancer.
  Individuals should consult a physician if any of the following symptoms appear: weak or interrupted flow of urine; urinating often (especially at night); difficulty urinating; pain or burning during urination; blood in the urine; or nagging pain in the back, hips, or pelvis. Often there are no symptoms of early cancer of the prostate.

  Colon and Rectum

  Of the cancers that affect the large intestine, about 70 percent occur in the colon and about 30 percent in the rectum. These cancers are the third most common cancers overall. Symptoms include blood in the stool, which can be tested for by a simple fecal occult blood test, or a change in bowel habits, such as severe constipation or diarrhea.

  Uterus (Corpus Uteri)

  The uterus is the sac in a woman's pelvis which allows a baby to develop from a fertilized egg and protects it until birth.
  Cancer of the uterus is the most common gynecologic malignancy. This cancer occurs infrequently in women under 40 years of age. It occurs most frequently after the age of 60. The presenting symptom is usually abnormal uterine bleeding. An endometrial biopsy or D&C is often performed to confirm the diagnosis.
  Currently, there has been little insight into the exact causes for uterine cancer. However, 10-25 percent of malignancies occur in women who received pelvic radiation five to 25 years earlier for benign bleeding. As in other cancers of its type, risk factors for uterine cancer include diabetes, hypertension, obesity, and improper estrogen levels.
  In addition to cancer types named after the primary site discussed above, there are many other examples such as brain cancer, testicular cancer, bladder cancer, and so on.

• Review: Categories of Cancer

  Here is what we have learned from Categories of Cancer:
• Cancers can be classified based either on histological type or their primary site (the location where the cancer originated).
• Derivation of cells and tissues starts with cell differentiation, which refers to the process of cells becoming arranged into three distinct germ layers: an outer ectoderm, an inner endoderm, and a mesoderm in between.
• All of the organs of the body develop or differentiate from these three primary germ layers.
• Tissue is composed of a group of cells that are similar in structure and perform one or more common functions.
• 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 the skin, lungs, female breasts, prostate, colon and rectum, and uterus.

• Cancer Diagnosis

  The diagnosis of cancer entails an attempt to accurately identify the anatomical site of origin of the malignancy and the type of cells involved. Cancer can arise in any organ or tissue in the body except fingernails, hair, and teeth.
  The site refers to the location of the cancer within the body. The body part in which cancer first develops is known as the primary site. A cancer's primary site may determine how the tumor will behave; whether and where it may spread (metastasize) and what symptoms it is most likely to cause. The most common sites in which cancer develops include the skin, lungs, female breasts, prostate, colon and rectum, and corpus uteri.
  Secondary site refers to the body part where metastasized cancer cells grow and form secondary tumors. A cancer is always described in terms of the primary site, even if it has spread to another part of the body. For instance, advanced breast cancer that has spread to the lymph nodes under the arm and to the bone and lungs is always considered breast cancer (and the spread to the lymph nodes, bones, and lungs describe the stage of the cancer).
  As is the case with other medical conditions, there are many signs and symptoms that may indicate the presence of cancer. These may be observed directly, through imaging technologies, or confirmed by lab tests. However, these signs and symptoms of cancer may resemble those of other conditions. For example, weight loss and abdominal pain can be caused by stomach cancer or an ulcer. Pink or reddish urine can be caused by kidney cancer or a kidney infection. A positive fecal occult blood test can indicate a variety of intestinal problems. A biopsy (removal of tissue for microscopic evaluation) is preferred to establish, or rule out, a diagnosis of cancer.
  Tissue samples can be easily retrieved from a tumor near the body's surface. If the mass is inaccessible, an imaging exam that enables a tumor to be located precisely and visualized may be ordered before the biopsy is performed.
  The histological type is determined by microscopic examination of suspected tissue that has been excised by biopsy or surgical resection. If the histological type is different from what is usually found in the tissue being examined, it can mean the cancer has spread to that area from some primary site. Metastasis can occur by direct extension, via the blood stream or the lymphatic system, or by seeding or implantation of cancer cells.
  A biopsy, together with advanced imaging technologies, may not only confirm the presence of cancer, but may also pinpoint the primary site and secondary site(s).
  It is also important to identify the cell type(s). Various histological types have different growth rates and dissimilar prognoses. More than one histological type of cell may be found in the same site. For example, a tumor whose primary site is skin can be a basal cell carcinoma, a squamous cell carcinoma, or a melanoma.
  Once cancer has been confirmed, the pathologist tries to determine how closely the cancer cells resemble healthy, mature cells. Such cells are said to be differentiated. Cancer cells that do not look like their healthy counterparts are called undifferentiated, or, because they often look like very immature cells, primitive. The pathologist assigns a pathological grade to a tumor according to how aggressive the tissue looks under the microscope. Tumor grades can be expressed in words or by a number. One set of terms consists of well differentiated (grade 1), moderately differentiated (grade 2), poorly differentiated (grade 3), or undifferentiated (grade 4). When tumors are graded by number (1 through 4), a grade-1 tumor has a better natural history than a grade-4 tumor does.
  Cancers are further classified according to stage. Staging describes how far a cancer has progressed based on the size of the primary tumor and whether and/or where it has spread. Go to the Summary Staging and Summary Stage 2000 training module for more details on cancer staging.
  In summary, a biopsy is the preferred method to confirm the diagnosis of cancer. Biopsies can provide information about histological type, classification, grade, potential aggressiveness and other information that may help determine the best treatment. More information regarding cancer treatment is provided in the Cancer Treatment training module.

• Review: Cancer Diagnosis

  Here is what we have learned from Cancer Diagnosis:
• A biopsy (removal of tissue for microscopic evaluation) is preferred to establish, or rule out, a diagnosis of cancer.
• Usually, a biopsy, together with advanced imaging technologies, can not only confirm the presence of cancer, but also pinpoint the primary site and secondary site(s) of the cancer, if any. A cancer's primary site may determine how the tumor will behave; whether and where it may spread, or metastasize; and what symptoms it is most likely to cause. A secondary site refers to the body part where metastasized cancer cells grow and form secondary tumors.
• Once a cancer has been confirmed, the pathologist often assigns a pathological grade to a tumor according to how malignant the tissue looks under the microscope. Cancers are further classified according to stage.

• Cancer Facts & the War on Cancer

  Cancer is a group of diseases characterized by uncontrolled growth and spread of abnormal cells. If the spread is not controlled, it can result in death. The following facts will help us understand the importance of the "War on Cancer."
  More than 1.2 million Americans develop cancer each year. A new cancer is diagnosed every 30 seconds in the United States. Since 1990, nearly 15 million new cancer cases have been diagnosed. These estimates do not include carcinoma in situ (non-invasive cancer) of any site except urinary bladder and do not include the basal and squamous cell skin cancers.
  Lung and prostate cancer are the top cancer killers for men in the United States. Lung and breast cancer are the top cancer killers for women in the United States. One in two men in the U.S. will be diagnosed with cancer at some time during his lifetime. One in three women in the US will be diagnosed with cancer at some time during her lifetime.
  Cancer is the second leading cause of death after heart disease in the United States. It is the primary cause of death in women between the ages of 35 and 74. About 8,000 American children will be diagnosed with cancer this year. Cancer is the chief cause of death in children between the ages of 1 and 14.
  If current trends continue, cancer is expected to be the leading cause of death in the United States by the year 2010. One in five persons in the US will die from cancer. Every three minutes, two people in the US die from cancer.
  Based on estimates of the National Institutes of Health, overall costs for cancer in the year 2000 was $180.2 billion: $60 billion for direct medical costs (total of all health expenditures); $15 billion for indirect morbidity costs (cost of lost productivity due to illness); and $105.2 billion for indirect mortality costs (cost of lost productivity due to premature death). Cancer-related costs account for about 10 percent of the total amount spent on disease treatment in the United States. Cancer is a major national burden.
  In 1970, the American people knew what they wanted -- a cure for the second-leading cause of death. President Nixon heard the voice of the people and the concerns of the medical profession. In his January 1971 State of the Union address, President Nixon made a special request for an additional $100 million to be added to the NCI budget for cancer research. In October 1971 he converted the Army's Fort Detrick, Maryland, biological warfare facility to a cancer research center. The resulting Frederick Cancer Research and Development Center eventually became an internationally recognized laboratory for cancer and AIDS research. However, President Nixon took a much bigger step when he signed the National Cancer Act into law on December 23, 1971, declaring, "I hope in the years ahead we will look back on this action today as the most significant action taken during my Administration."
  After more than three decades, the "War on Cancer," declared by President Nixon in 1971 with the enactment of the National Cancer Act, is still going on in this country. The Question is: "Are we winning the war?"
  Unfortunately, there is no simple answer to the question. The good news is that since Nixon's initiative, there have been incredible advances in cancer detection, prevention, and treatment. Since the mid 1990s, the cancer death rate has been decreasing steadily. As one cancer experts puts it: "It's just amazing those who are making it and are living, whereas 10 years ago these same people would not have lived." A diagnosis of cancer once was the virtual equivalent of a death sentence. Today, nearly half of all cancer patients can expect to live for five or more years after the diagnosis of cancer.
  However, scientists are still not able to pinpoint a "cause" for cancer. Instead, cancer researchers now believe that cancer can be triggered by many factors, such as our genetics, diet and occupation. We know that our chances of developing cancer can be significantly reduced if we choose to live a healthy lifestyle, not smoke and avoid certain foods.
  Finally, while a "cure" for cancer has not yet been found, scientists are more confident than ever that further breakthroughs in cancer detection and therapy are not far away, allowing us to effectively control the disease.

• Review: The War on Cancer

  To illustrate how important the "War On Cancer" is in this country, some sobering facts about cancer are provided in The War On Cancer:
• More than 1.2 million Americans develop cancer each year.
• Since 1990, nearly 15 million new cancer cases have been diagnosed in the U.S.
• Cancer is the second leading cause of death after heart disease in the United States, but it is the major cause of death in women between the ages of 35 and 74. One in two men in the U.S. will be diagnosed with cancer at some time during his lifetime.
• Cancer is the chief cause of death in children between the ages of 1 and 14.
• Cancer-related costs account for about 10 percent of the total amount of money spent on disease treatment in the United States.
•