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Glossary - H


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  • Hair Follicle

    (… FAH-lih-kul)

    A shaft or opening on the surface of the skin through which hair grows.

  • Harvest

    The removal of a donor's bone marrow prior to bone marrow transplant.

  • HDAC inhibitor


    A substance that causes a chemical change that stops tumor cells from dividing. HDAC inhibitors are being studied in the treatment of cancer. Also called histone deacetylase inhibitor.

  • Head and neck cancer

    (... KAN-ser)

    Cancer that arises in the head or neck region (in the nasal cavity, sinuses, lips, mouth, salivary glands, throat, or larynx [voice box]).

  • Health History

    (helth HIH-stuh-ree)

    A record of information about a persons health. A personal health history may include information about allergies, illnesses, surgeries, immunizations, and results of physical exams and tests. It may also include information about medicines taken and health habits, such as diet and exercise. A family health history includes health information about a persons close family members (parents, grandparents, children, brothers, and sisters). This includes their current and past illnesses. A family health history may show a pattern of certain diseases in a family. Also called medical history.

  • Healthcare provider

    (HELTH-kayr proh-VY-der)

    A licensed person or organization that provides healthcare services.

  • Healthcare proxy

    (HELTH-kayr PRAK-see)

    A type of advance directive that gives a person (such as a relative, lawyer, or friend) the authority to make healthcare decisions for another person. It becomes active when that person loses the ability to make decisions for himself or herself. Also called HCP.

  • Heart attack

    A heart attack happens when the flow of oxygen-rich blood in one or more of the coronary arteries, which supply the heart muscle, suddenly becomes blocked, and a section of heart muscle cant get enough oxygen. The blockage is usually caused when a plaque ruptures. If blood flow isnt restored quickly, either by a medicine that dissolves the blockage or a catheter placed within the artery that physically opens the blockage, the section of heart muscle begins to die.

  • Hematocrit


    The amount of whole blood that is made up of red blood cells. It depends on the number and size of red blood cells. A hematocrit test is usually part of a complete blood count (CBC). It may be used to check for conditions such as anemia, dehydration, malnutrition, and leukemia. Also called HCT.

  • Hematologist


    A doctor who has special training in diagnosing and treating blood disorders.

  • Hematology

    A medical science that deals with the blood and blood-forming organs.

  • Hematology/oncology

    The branch of medical science that treats disorders of the blood, blood forming tissues and tumor cells.

  • Hematoma


    A pool of mostly clotted blood that forms in an organ, tissue, or body space. A hematoma is usually caused by a broken blood vessel that was damaged by surgery or an injury. It can occur anywhere in the body, including the brain. Most hematomas are small and go away on their own, but some may need to be removed by surgery.

  • Hematuria


    Blood in the urine; urine may be pink, red, or brown (coke colored).

  • Hemoglobin


    A protein inside red blood cells that carries oxygen from the lungs to tissues and organs in the body and carries carbon dioxide back to the lungs. Testing for the amount of hemoglobin in the blood is usually part of a complete blood cell (CBC) test.

  • Hemolysis


    The breakdown of red blood cells. Some diseases, medicines, and toxins may cause red blood cells to break down more quickly than usual.

  • Hemorrhage


    In medicine, loss of blood from damaged blood vessels. A hemorrhage may be internal or external, and usually involves a lot of bleeding in a short time.

  • Hemorrhagic cystitis

    (HEH-muh-RA-jik sis-TY-tis)

    A condition in which the lining of the bladder becomes inflamed and starts to bleed. The blood can be seen in the urine. Symptoms include pain and a burning feeling while urinating, feeling a need to urinate often, and being unable to control the flow of urine. Hemorrhagic cystitis may be caused by anticancer drugs, radiation therapy, infection, or being exposed to chemicals, such as dyes or insecticides.

  • Hemorrhoids


    An enlarged or swollen blood vessel, usually located near the anus or the rectum.

  • Heparin


    A substance that slows the formation of blood clots. Heparin is made by the liver, lungs, and other tissues in the body and can also made in the laboratory. Heparin may be injected into muscle or blood to prevent or break up blood clots. It is a type of anticoagulant.

  • Hepatitis


    Disease of the liver causing inflammation. Symptoms include an enlarged liver, fever, nausea, vomiting, abdominal pain, and dark urine.

  • Hepatitis B

    (HEH-puh-TY-tis ...)

    A virus that causes hepatitis (inflammation of the liver). It is carried and passed to others through the blood and other body fluids. Different ways the virus is spread include sharing needles with an infected person and being stuck accidentally by a needle contaminated with the virus. Infants born to infected mothers may also become infected with the virus. Although many patients who are infected with hepatitis B virus may not have symptoms, long-term infection may lead to cirrhosis (scarring of the liver) and liver cancer. Also called HBV.

  • Hepatoblastoma


    A type of liver tumor that occurs in infants and children.

  • Hepatocellular carcinoma

    A type of adenocarcinoma and the most common type of liver tumor.

  • Herbal supplement

    (ER-bul SUH-pleh-ment)

    A product made from a plant that is thought to be useful in treating disease or staying healthy. Herbal supplements are taken by mouth.

  • Hereditary

    In medicine, describes the passing of genetic information from parent to child through the genes in sperm and egg cells. Also called inherited.

  • HICKMAN® catheter

    See BROVIAC® catheter.

  • High blood pressure

    (hy blud PREH-sher)

    A blood pressure of 140/90 or higher. High blood pressure usually has no symptoms. It can harm the arteries and cause an increase in the risk of stroke, heart attack, kidney failure, and blindness. Also called hypertension.

  • High-dose chemotherapy

    (hy-dose kee-moh-THAYR-uh-pee)

    An intensive drug treatment to kill cancer cells, but that also destroys the bone marrow and can cause other severe side effects. High-dose chemotherapy is usually followed by bone marrow or stem cell transplantation to rebuild the bone marrow.

  • High-dose radiation

    (hy-dose RAY-dee-AY-shun)

    An amount of radiation that is greater than that given in typical radiation therapy. High-dose radiation is precisely directed at the tumor to avoid damaging healthy tissue, and may kill more cancer cells in fewer treatments. Also called HDR.

  • High-grade

    (hy grayd)

    A term used to describe cells and tissue that look abnormal under a microscope. High-grade cancer cells tend to grow and spread more quickly than low-grade cancer cells. Cancer grade may be used to help plan treatment and determine prognosis. High-grade cancers usually have a worse prognosis than low-grade cancers and may need treatment right away or treatment that is more aggressive (intensive).

  • High-risk cancer

    (hy-risk KAN-ser)

    Cancer that is likely to recur (come back), or spread.

  • Histology


    The study of tissues and cells under a microscope.

  • HIV

    The cause of acquired immunodeficiency syndrome (AIDS). Also called human immunodeficiency virus.

  • Hives


    Itchy, raised red areas on the skin. Hives are caused by a reaction to certain foods, drugs, infections, or emotional stress. Also called urticaria.

  • Hodgkin lymphoma

    HOJ-kin lim-FOH-muh

    A cancer of the immune system that is marked by the presence of a type of cell called the Reed-Sternberg cell. The two major types of Hodgkin lymphoma are classical Hodgkin lymphoma and nodular lymphocyte-predominant Hodgkin lymphoma. Symptoms include the painless enlargement of lymph nodes, spleen, or other immune tissue. Other symptoms include fever, weight loss, fatigue, or night sweats. Also called Hodgkin disease.

  • Hormone


    One of many substances made by glands in the body. Hormones circulate in the bloodstream and control the actions of certain cells or organs. Some hormones can also be made in the laboratory.

  • Hormone-refractory


    In medicine, describes a disease or condition that does not respond to treatment with hormones. Also called hormone-resistant.

  • Hormone replacement therapy

    (HOR-mone reh-PLAYS-ment THAYR-uh-pee)

    Treatment with hormones to replace natural hormones when the body does not make enough. For example, hormone replacement therapy may be given when the thyroid gland does not make enough thyroid hormone or when the pituitary gland does not make enough growth hormone. Or, it may be given to women after menopause to replace the hormones estrogen and progesterone that are no longer made by the body. Also called HRT.

  • Hormone responsive

    (HOR-mone reh-SPONT-siv)

    In oncology, describes cancer that responds to hormone treatment.

  • Hormone therapy

    (HOR-mone THAYR-uh-pee)

    Treatment that adds, blocks, or removes hormones. For certain conditions (such as diabetes or menopause), hormones are given to adjust low hormone levels. To slow or stop the growth of certain cancers (such as prostate and breast cancer), synthetic hormones or other drugs may be given to block the bodys natural hormones. Sometimes surgery is needed to remove the gland that makes a certain hormone. Also called endocrine therapy, hormonal therapy, and hormone treatment.

  • Horner syndrome


    A condition in which one side of the face is flushed, does not produce sweat, and has a constricted pupil and drooping eyelid. It can be caused by an injury to, or paralysis of, nerves in the neck, or by a tumor.

  • Hospice


    A program that gives special care to people who are near the end of life and have stopped treatment to cure or control their disease. Hospice offers physical, emotional, social, and spiritual support for patients and their families. The main goal of hospice care is to control pain and other symptoms of illness so patients can be as comfortable and alert as possible. It is usually given at home, but may also be given in a hospice center, hospital, or nursing home.

  • Host cell

    (... sel)

    A cell that is infected by a virus or another type of microorganism.

  • Human leukocyte antigens

    HYOO-mun LOO-koh-site AN-tih-jen

    Antigens that appear on white blood cells as well as cells of almost all other tissues. By typing for HL-A antigens, donors and recipients of white blood cells, platelets, and organs can be "matched" insuring good performance and survival of transfused and transplanted cells.

  • Hydration


    The process of combining with water. In medicine, the process of giving fluids needed by the body.

  • Hydrocephalus


    The abnormal buildup of cerebrospinal fluid in the ventricles of the brain.

  • Hydrocortisone


    A drug used to relieve the symptoms of certain hormone shortages and to suppress an immune response.

  • Hyper

    Prefix meaning ""more than"" normal.

  • Hyperactivity


    A higher than normal level of activity. Hyperactivity can be used to describe the increased action of a body function, such as hormone production, or behavior. A person who is hyperactive may seem to be always moving or fidgeting, impulsive, unable to concentrate, and talking too much.

  • Hyperalimentation


    A form of nutrition that is delivered into a vein. Hyperalimentation does not use the digestive system. It may be given to people who are unable to absorb nutrients through the intestinal tract because of vomiting that won't stop, severe diarrhea, or intestinal disease. It may also be given to those undergoing high-dose chemotherapy or radiation and bone marrow transplantation. It is possible to give all of the protein, calories, vitamins and minerals a person needs using hyperalimentation. Also called parenteral nutrition, total parenteral nutrition, and TPN.

  • Hypercellular

    More than the normal number of cells.

  • Hyperglycemia


    Higher than normal amount of glucose (a type of sugar) in the blood. Hyperglycemia can be a sign of diabetes or other conditions. Also called high blood sugar.

  • Hyperparathyroidism


    A condition in which the parathyroid gland (one of four pea-sized organs found on the thyroid) makes too much parathyroid hormone. This causes a loss of calcium from the bones and an increased level of calcium in the blood. Symptoms include bone pain and kidney problems.

  • Hypersensitivity


    An exaggerated response by the immune system to a drug or other substance.

  • Hypertension


    A blood pressure of 140/90 or higher. Hypertension usually has no symptoms. It can harm the arteries and cause an increase in the risk of stroke, heart attack, kidney failure, and blindness. Also called high blood pressure.

  • Hypnosis


    A trance-like state in which a person becomes more aware and focused on particular thoughts, feelings, images, sensations, or behaviors. While under hypnosis, a person may feel calm, relaxed, and more open to suggestion. Hypnosis is usually done with the help of a specially trained therapist. It may be used to help relieve stress, anxiety, and pain, and to help a person quit smoking or lose weight. Hypnosis is a type of complementary and alternative medicine (CAM).

  • Hypo

    Prefix meaning ""too little."".

  • Hypocalcemia

    Too little calcium in the blood.

  • Hypocellular

    Less than the normal number of cells.

  • Hypofractionated radiation therapy

    (HY-poh-FRAK-shuh-NAY-ted RAY-dee-AY-shun THAYR-uh-pee)

    Radiation treatment in which the total dose of radiation is divided into large doses and treatments are given once a day or less often. Hypofractionated radiation therapy is given over a shorter period of time (fewer days or weeks) than standard radiation therapy.

  • Hypoglycemia


    Abnormally low blood sugar.

  • Hypokalemia


    Too little potassium in the blood.

  • Hypotension


    Abnormally low blood pressure.

  • Hypothalamus


    The area of the brain that controls body temperature, hunger, and thirst.

  • Hypothyroidism


    Too little thyroid hormone. Symptoms include weight gain, constipation, dry skin, and sensitivity to the cold. Also called underactive thyroid.