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A harmful, cancer-causing chemical made by certain types of Aspergillus mold that may be found on poorly stored grains and nuts. Consumption of foods contaminated with aflatoxin is an important risk factor for hepatocellular (liver) cancer.

Age-specific rate:
A rate for a specified age group, in which the numerator and denominator refer to the same age group.

A technique that facilitates comparison of incidence (or mortality) rates between populations or over time, adjusting for any differences in the age distributions of the general population in the countries or regions being compared. Age standardization can also be used to facilitate comparison of cancer survival between populations or over time: this requires adjustment for any differences in the age distributions of the cancer patients being compared.

A natural material that is made of tiny fibers and used in insulation and as a fire retardant. Asbestos exposure is an important risk factor for cancer, especially mesothelioma (lining of the chest, abdomen and heart) and also lung cancer.

Benign tumor:An abnormal growth that is not cancer and does not spread to other areas of the body.

Body mass index (BMI):
A measure of a person’s weight in relation to his or her height, calculated as weight in kilograms divided by height in meters squared.

A disease in which abnormal cells divide uncontrollably. Cancer cells can invade nearby tissues and spread through the bloodstream and lymphatic system to other parts of the body.

Cancer registry:
An institution that performs the systematic collection and maintenance of a file or register of all cancer cases occurring in a defined population. Registries continuously and systematically collect information from various data sources on the personal characteristics of cancer patients (e.g. age, sex, and race) and the clinical and pathological characteristics (e.g. stage, histologic classification) of the cancers.

Cancer screening programs:
Programs organized at a national or regional level that aim to decrease the incidence and mortality of a specific type of cancer by identifying precancerous lesions or tumors at an early stage, when they can be effectively treated. Programs usually have: 1) an explicit policy; 2) a team responsible for organizing the screening and delivering appropriate healthcare; and 3) a structure for assuring quality screening and follow-up of abnormal screening tests.

Any agent —chemical, physical or biological—that causes cancer. Examples include tobacco smoke, asbestos, human papillomavirus (HPV), and ultraviolet (UV) radiation.

A cancerous tumor that begins in the lining layer (epithelial cells) of organs. At least 80% of all cancers are carcinomas.

Treatment with a drug or drugs to destroy cancer cells. Chemotherapy may be used, either alone or in combination with surgery or radiation treatment, to treat cancer when it is at an early stage, when the cancer has spread, when the cancer has come back (recurred), or when there is a strong chance that the cancer could recur.

Examination of the large bowel with a long, flexible, lighted tube called a colonoscope. The physician looks for polyps or early cancers during the exam, and removes them using a wire passed through the colonoscope.

Computerized tomography (CT):
A series of detailed pictures of areas inside the body taken from different angles; the pictures are created by a computer linked to an x-ray machine. Also called computerized axial tomography (CAT) scan. A special kind of CT machine, the spiral CT, has been used to look for early lung cancer.

The process of identifying a disease by its signs and symptoms, as well as medical tests and tissue sampling and examination as needed.

Organic chemical byproducts of industrial processes; considered highly toxic environmental pollutants due to their effects on the immune and endocrine systems and on encouraging tumor growth.

Direct costs:
Expenditures for medical procedures and services associated with the treatment and care of people with cancer.

Disability-adjusted life year (DALY):
A measurement of the years of healthy life lost due to disease in a population. DALYs are the sum of two components: the years of life lost due to premature death, and the years of life lost due to disability.

E-cigarette: A device that contains a solution of nicotine, flavorings, and other chemicals that turns into a mist that can be inhaled into the lungs. Also called electronic cigarette.

Endometrial cancer:
Cancer of the layer of tissue that lines the uterus.

Occurrence of an illness, condition, or behavior that affects many people in the same region during a specified period of time. To constitute an epidemic, this occurrence must exceed normal occurrence of the disease in the region.

Estradiol: A form of the hormone estrogen.

Fecal occult blood test (FOBT):
A test used to screen for large bowel cancer. It looks for blood in the stools, the presence of which may be a sign of cancer.

Helicobacter pylori (H. pylori):
A type of bacterium that causes inflammation and ulcers in the stomach or small intestine. People with H. pylori infections may be more likely to develop cancer in the stomach.

Hematopoietic system:
Organs and tissues involved in the production of blood, including the bone marrow, lymph nodes, spleen, and tonsils.

Hepatitis B and C viruses (HBV and HCV):
Viruses that cause hepatitis, a condition that is characterized by inflammation of the liver. Long-term infection may lead to cirrhosis (scarring of the liver) and liver cancer. Persons infected with HCV may also have an increased risk for certain types of non-Hodgkin lymphoma.

Hepatocellular carcinoma:
The most common type of cancer originating in the liver.

High-/middle-/low-income country:
For the 2020 fiscal year, according to the World Bank, a high-income country has a gross national income (GNI) per capita of more than US$12,375; a middle-income country between US$1026 and US$12,375; and a low-income country less than US$1025.

Hormone replacement therapy (HRT):
Hormones (estrogen, progesterone, or other types) given to women after menopause to replace the hormones no longer produced by the ovaries. HRT can be a risk factor for cancers of the endometrium and breast.

Human development index (HDI):
A measure of health, education and income at the country level produced by the United Nations Development Programme as an alternative to purely economic assessments of national progress, such as GDP growth.

Human herpesvirus 8 (HHV-8):
A type of virus that causes Kaposi sarcoma. Patients with acquired immunodeficiency syndrome frequently suffer from HHV-8-associated diseases. Infection with HHV-8 can also cause certain types of lymphoma and severe lymph node enlargement, known as Castleman’s disease. HHV-8 is also known as Kaposi sarcoma-associated herpesvirus, or KSHV.

Human immunodeficiency virus (HIV):
The virus that causes acquired immune deficiency syndrome (AIDS). It is transmitted through blood and other body fluids, and infants born to infected mothers may also become infected. Infection with both HIV and HHV-8 increases the risk of developing Kaposi sarcoma.

Human papillomavirus (HPV):
A type of virus that can cause abnormal tissue growth (for example, warts) and other changes to cells. Long-term infection with certain types of human papillomavirus (e.g., types 16 and 18) can cause cervical cancer. HPV is also a risk factor for anal, vaginal, vulvar, penile, oropharyngeal, and squamous cell skin cancers. It is transmitted through sexual contact.

The number of new cases arising in a given period in a specified population. This information, collected routinely by population-based cancer registries, can be expressed as an absolute number of cases per year or as a rate per 100,000 persons per year. Incidence rates can be expressed for all ages combined, or for selected age ranges. They can also be expressed for each sex, or for both sexes combined.

Kaposi sarcoma:
A type of cancer characterized by the abnormal growth of blood vessels that develop into lesions on the skin, lymph nodes, lining of the mouth, nose, and throat, and other tissues of the body. It is caused by human herpesvirus-8 (HHV-8). The risk of developing Kaposi sarcoma in a person who has HHV-8 increases significantly if the person is also infected with human immunodeficiency virus (HIV).

Keratinocyte (nonmelanoma) skin cancer:
Also known as basal or squamous cell skin cancer. A cancer that occurs in keratinocyte cells, which are located in the epidermis (top layer of skin) and are responsible for producing keratin. Keratinocytes are divided into squamous cells on the surface of the epidermis and basal cells located within the deeper basal layer of the epidermis.

A cancer of the blood or blood-forming organs.

Surgery to remove a breast lump or tumor and a small amount of surrounding normal tissue.

A cancer of the lymphatic system. The lymphatic system is a network of thin vessels and nodes throughout the body. The two main types of lymphoma are Hodgkin lymphoma (or disease) and non-Hodgkin lymphoma.

Malignant tumor:
A mass of cancer cells that may invade surrounding tissues or spread (metastasize) to distant areas of the body. Synonymous with cancer.

Mammography: A breast cancer screening method using an x-ray of the breast.

Surgery to remove the entire breast. There are different types of mastectomy that differ in the amount of tissue and lymph nodes removed.

A cancerous (malignant) tumor that begins in the cells that produce the skin coloring (melanocytes). Melanoma is almost always curable in its early stages. However, it is likely to spread, and once it has spread to other parts of the body the likelihood of cure decreases.

The first menstrual period, usually occurring during puberty.

The time period marked by the permanent cessation of menstruation, usually occurring between the ages of 45 and 55 years.

A benign (not cancer) or malignant (cancer) tumor affecting the lining of the chest or abdomen. Exposure to asbestos particles in the air increases the risk of developing malignant mesothelioma, which is extremely lethal.

The distant spread of cancer from its primary site to other places in the body.

Any departure from physiological or psychological well-being. Measures of morbidity for people living with cancer may include disability, pain, time away from work, or days spent in the hospital.

The number of deaths occurring in a given period in a specified population. Information on all deaths is collected as part of vital registration; in many countries this is required by law. It can be expressed as an absolute number of deaths per year or as a rate per 100,000 persons per year. Mortality rates can be expressed for all ages combined, or for selected age ranges. They can also be expressed for each sex, or for both sexes combined.

An abnormal growth (tumor) that starts from a single altered cell; a neoplasm may be benign or malignant. Cancer is a malignant neoplasm.

Cancer that arises in immature nerve cells; affects mostly infants and children.

Persons who are considered overweight have a body mass index (BMI) greater than 25; a BMI greater than 30 is considered obese.

Particulate matter:
Microscopic solid or liquid particles associated with the atmosphere that can penetrate the lungs and cause damage that can lead to lung cancer. Particulate matter can be naturally occurring (e.g. originating from volcanoes or dust storms) or synthetic (e.g. vehicle emissions). The smallest class of particulate matter (<2.5 micrometers diameter) is the deadliest.

Palliative care:
An approach that aims to improve the quality of life for patients and families facing the problems associated with life-threatening cancers. It provides for prevention and relief of suffering through treatment for pain and other symptoms as well as through spiritual and psychosocial support, at the time of cancer diagnosis, through the end of life, and during family bereavement.

The overall prevalence is the number of persons in a defined population who have been diagnosed with a specific type of cancer, and who are still alive at  a given point in time (cancer survivors). Five-year prevalence includes only cancer survivors who were diagnosed up to 5 years earlier. It is a particularly useful measure of the cancer burden, because for many cancers, patients who are still alive five years after diagnosis will often have a very good prognosis. Exceptions include women with breast cancer, who continue to die from the disease more than 5 years after diagnosis.

Prediction of the course of cancer, and the outlook for a cure of the cancer.  A general term for prediction of the course of cancer, and the outlook for long-term survival.

The use of radiation treatment to kill cancer cells or stop them from dividing.

A radioactive gas that is released by uranium—a substance found in soil and rock—and is an important risk factor for lung cancer.

see Incidence and Mortality

A rare form of eye cancer that affects the retina of infants and young children.

A cancer of the bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue.

An examination to help find cancer or polyps within the rectum and distal part of the colon. A slender, hollow, lighted tube is placed into the rectum, allowing the physician to look for polyps or other abnormalities. The sigmoidoscope is shorter than the colonoscope.

Solar irradiation:
See UV radiation.

Solid fuels:
Solid materials burned usually for heating purposes, including wood, peat, charcoal, coal, and grains. In certain conditions, excess exposure can be an important risk factor for lung cancer.

Survival is estimated as the probability of survival up to a specified time (e.g., 1, 3, or 5 years) following a cancer diagnosis. It is usually estimated from population-based cancer registry data, and expressed as a percentage.  Cancer patients can die from other causes than their cancer (“background mortality”). Comparisons of cancer survival between populations or over time are therefore adjusted for background mortality: this is usually referred to as “net survival”. Survival is a widely used measure of cancer prognosis.

Systemic therapy: Treatment using substances that travel through the bloodstream, reaching and affecting cells all over the body.

Targeted therapy:
A cancer treatment that uses drugs or other substances to identify and attack cancer cells while avoiding harm to normal cells better than many other cancer treatments. Some targeted therapies block the mechanisms involved in the growth and spread of cancer cells. Other types of targeted therapies help the immune system kill cancer cells or deliver toxic substances directly to cancer cells.

Ultraviolet (UV) radiation:
Invisible rays that are part of the energy that comes from the sun. UV radiation also comes from sun lamps and tanning beds. UV radiation can damage the skin, lead to premature aging, and cause melanoma and other types of skin cancer.

Vital registration:
The continuous, permanent and universal recording of the occurrence and characteristics of vital events (e.g., births and deaths) in the population. Vital registration is often required by law, or by decree or regulation. In many countries, a diagnosis of cancer must also be registered by law, as part of public health surveillance of disease.

Wilms tumor:
A type of kidney cancer that usually occurs in children younger than 5 years of age.

Years of life lost (YLL):
A statistic that measures the burden of premature death in a population due to a specific cause (such as cancer) within a specified time frame by aggregating the difference between expected life span and years lived among those who died due to the cause of interest.

Please refer to the U.S. National Cancer Institute’s “Dictionary of Cancer Terms” for additional definitions.