Cancer (Malignant Neoplasms)

Cancer /ˈkænsər/, known medically as a malignant neoplasm, is a broad group of various diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the body through the lymphatic system or bloodstream. Not all tumors are cancerous. Benign tumors do not grow uncontrollably, do not invade neighboring tissues, and do not spread throughout the body. There are over 200 different known cancers that afflict humans.^[1]

Determining what causes cancer is complex. Many things are known to increase the risk of cancer, including tobacco use, certain infections, radiation, lack of physical activity, obesity, and environmental pollutants.^[2] These can directly damage genes or combine with existing genetic faults within cells to cause the disease.^[3] Approximately five to ten percent of cancers are entirely hereditary.

Cancer can be detected in a number of ways, including the presence of certain signs and symptoms, screening tests, or medical imaging. Once a possible cancer is detected it is diagnosed by microscopic examination of a tissue sample. Cancer is usually treated with chemotherapy, radiation therapy and surgery. The chances of surviving the disease vary greatly by the type and location of the cancer and the extent of disease at the start of treatment. While cancer can affect people of all ages, and a few types of cancer are more common in children, the risk of developing cancer generally increases with age. In 2007, cancer caused about 13% of all human deaths worldwide (7.9 million). Rates are rising as more people live to an old age and as mass lifestyle changes occur in the developing world.^[4]

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Signs and symptoms

When cancer begins it invariably produces no symptoms with signs and symptoms only appearing as the mass continues to grow or ulcerates. The findings that result depends on the type and location of the cancer. Few symptoms are specific, with many of them also frequently occurring in individuals who have other conditions. Cancer is the new "great imitator". Thus it is not uncommon for people diagnosed with cancer to have been treated for other diseases to which it was assumed their symptoms were due.

Local effects

Local symptoms may occur due to the mass of the tumor or its ulceration. For example mass effects from lung cancer can cause blockage of the bronchus resulting in cough or pneumonia, esophageal cancer can cause narrowing of the esophagus making it difficult or painful to swallow, and colorectal cancer may lead to narrowing or blockages in the bowel resulting in changes in bowel habits. Masses of breast or testicles may be easily felt. Ulceration can cause bleeding which, if it occurs in the lung, will lead to coughing up blood, in the bowels to anemia or rectal bleeding, in the bladder to blood in the urine, and in the uterus to vaginal bleeding. Although localized pain may occurs in advanced cancer, the initial swelling is usually painless. Some cancers can cause build up of fluid within the chest or abdomen.

Systemic symptoms

General symptoms occur due to distant effects of the cancer that are not related to direct or metastatic spread. These may include: unintentional weight loss, fever, being excessively tired, and changes to the skin. Hodgkin disease, leukemias, and cancers of the liver or kidney can cause a persistent fever of unknown origin.
Specific constellations of systemic symptoms, termed paraneoplastic phenomena, may occur with some cancers. Examples include the appearance of myasthenia gravis in thymoma and clubbing in lung cancer.

Metastasis

Symptoms of metastasis are due to the spread of cancer to other locations in the body. They can include enlarged lymph nodes (which can be felt or sometimes seen under the skin and are typically hard), hepatomegaly (enlarged liver) or splenomegaly (enlarged spleen) which can be felt in the abdomen, pain or fracture of affected bones, and neurological symptoms.

Diagnosis

Most cancers are initially recognized either because of the appearance of signs or symptoms or through screening. Neither of these lead to a definitive diagnosis, which requires the examination of a tissue sample by a pathologist. People with suspected cancer are investigated with medical tests. These commonly include blood tests, X-rays, CT scans and endoscopy.

Classification

Further information: List of cancer types and List of oncology-related terms

Cancers are classified by the type of cell that the tumor cells resemble and is therefore presumed to be the origin of the tumor. These types include:

• Carcinoma: Cancers derived from epithelial cells. This group includes many of the most common cancers, particularly in the aged, and include nearly all those developing in the breast, prostate, lung, pancreas, and colon.
• Sarcoma: Cancers arising from connective tissue (i.e. bone, cartilage, fat, nerve), each of which develop from cells originating in mesenchymal cells outside the bone marrow.
• Lymphoma and leukemia: These two classes of cancer arise from hematopoietic (blood-forming) cells that leave the marrow and tend to mature in the lymph nodes and blood, respectively. Leukemia is the most common type of cancer in children accounting for about 30%.
• Germ cell tumor: Cancers derived from pluripotent cells, most often presenting in the testicle or the ovary (seminoma and dysgerminoma, respectively).
• Blastoma: Cancers derived from immature "precursor" cells or embryonic tissue. Blastomas are more common in children than in older adults.

Cancers are usually named using -carcinoma, -sarcoma or -blastoma as a suffix, with the Latin or Greek word for the organ or tissue of origin as the root. For example, cancers of the liver parenchyma arising from malignant epithelial cells is called hepatocarcinoma, while a malignancy arising from primitive liver precursor cells is called a hepatoblastoma, and a cancer arising from fat cells is called a liposarcoma. For some common cancers, the English organ name is used. For example, the most common type of breast cancer is called ductal carcinoma of the breast. Here, the adjective ductal refers to the appearance of the cancer under the microscope, which suggests that it has originated in the milk ducts.

Benign tumors (which are not cancers) are named using -oma as a suffix with the organ name as the root. For example, a benign tumor of smooth muscle cells is called a leiomyoma (the common name of this frequently occurring benign tumor in the uterus is fibroid). Confusingly, some types of cancer also use the -oma suffix, examples including melanoma and seminoma.

Some types of cancer are named for the size and shape of the cells under a microscope, such as giant cell carcinoma, spindle cell carcinoma, and small cell carcinoma.

Pathology

The tissue diagnosis given by the pathologist indicates the type of cell that is proliferating, its histological grade, genetic abnormalities, and other features of the tumor. Together, this information is useful to evaluate the prognosis of the patient and to choose the best treatment. Cytogenetics and immunohistochemistry are other types of testing that the pathologist may perform on the tissue specimen. These tests may provide information about the molecular changes (such as mutations, fusion genes, and numerical chromosome changes) that has happened in the cancer cells, and may thus also indicate the future behavior of the cancer (prognosis) and best treatment.

Who is at risk of getting cancer?

Cancer can affect all walks of life regardless of background and economic status. However, cancer risk is higher if you:

A. Aged over 55 years

Cancer is a disease that increases the risk as you age. The more senior you are, the greater your risk of cancer. In children and teenagers, the cancer is relatively rare. More than half of cancers strike after age sixty. The main reason why new cancers arise in old age is a slow growth. Development of cancer is sometimes very slow and can only be detected at an advanced stage. Cancer can develop for years without you knowing it.

2. Overweight (obese)

If your BMI is 30 or more, you have obesity. Experts have concluded that cancer of the colon, breast, endometrium (lining of the uterus), kidney, and esophagus are associated with obesity. Several studies have also reported an association between obesity and cancer of the gallbladder, ovaries, and pancreas.

Prevent weight gain may reduce the risk of cancer. The experts advise you to maintain healthy eating habits and physical activity early in life to prevent overweight and obesity. Those who are overweight or obese are advised to avoid additional weight gain, and lose weight through low calorie diet and exercise. Even the weight loss is only 5-10 percent of the total weight can be beneficial to health.

3. Smoke

You must have known that smoking increases the risk of lung cancer. Nearly 90% of deaths from lung cancer in men and 80% in women are caused by smoking. However, note also that smoking may trigger development of other cancers, namely cancer of the oral cavity, larynx, esophagus, bladder, stomach, kidney, cervix, and pancreas. Cigarette smoke contains over 4000 chemicals. More than 40 of which are cancer-triggering substances (carcinogens).

4. Cancer have a genetic predisposition

In most patients, the cause of sporadic cancer is the result of progressive accumulation of genetic mutations and / or epigenetic changes in a lifetime. This is called somatic mutations, which affect only certain tissues and not inherited. On the other fraction, cancers caused by inherited gene defects. Some people are born with a gene mutation inherited from their mother or father. Defective gene is a tumor suppressor gene usually makes them susceptible to cancer.

Patients with inherited cancer often have cancer at a younger age than the general population and 50% chance to pass on their susceptibility to its offspring.