H. pyloriA type of bacterium that causes inflammation and ulcers in the stomach or small intestine. People with H.
hA20A monoclonal antibody that is being studied in the treatment of refractory B-cell non-Hodgkin lymphoma.
HAARTHighly active antiretroviral therapy. Treatment for human immunodeficiency virus (HIV) infection that uses a combination of several antiretroviral drugs.
hair follicle(FOL-i-kul) A shaft or opening on the surface of the skin through which hair grows.
hairy cell leukemia(HAYR-ee SEL loo-KEE-mee-uh) A rare type of leukemia in which abnormal B-lymphocytes (a type of white blood cell) are present in the bone marrow, spleen…
Haldol(HAL-dol) A drug used to treat certain mental and neurological disorders. It is also being studied in the treatment of nausea and vomiting caused by some…
half-sibling(HAF-SIB-ling) A person's brother or sister who has one parent in common.
hallucination(huh-LOO-sih-NAY-shun) A sight, sound, smell, taste, or touch that a person believes to be real but is not real.
halofuginone hydrobromideA substance that is being studied for its ability to slow the growth of connective tissue and prevent the growth of new blood vessels to a solid tumor.
haloperidol(ha-loh-PAYR-ih-dol) A drug used to treat certain mental and neurological disorders.
Halsted radical mastectomy(HAWL-sted RA-dih-kul ma-STEK-toh-mee) Surgery for breast cancer in which the breast, chest muscles, and all of the lymph nodes under the arm are removed.
hamartoma(ham-ar-TOE-ma) A benign (noncancerous) growth made up of an abnormal mixture of cells and tissues normally found in the area of the body where the growth…
hand-foot syndromeA condition marked by pain, swelling, numbness, tingling, or redness of the hands or feet.
happy majorA plant whose seeds and root have been used in some cultures to treat certain medical problems. It may have antioxidant effects.
hard palate(PAL-et) The front, bony part of the roof of the mouth.
hawthorn fruitThe fruit of the hawthorn tree or bush. It has been used in some cultures to treat certain medical problems, including heart problems and gastrointestinal…
hazard ratio(HA-zurd RAY-shee-oh) A measure of how often a particular event happens in one group compared to how often it happens in another group, over time.
HCAA chemical that is formed when meat, poultry, or fish is cooked at high temperatures, such as frying, broiling, and barbecuing.
HCD20A monoclonal antibody that is being studied in the treatment of refractory B-cell non-Hodgkin lymphoma.
HCPHealthcare proxy. A type of advance directive that gives a person (such as a relative, lawyer, or friend) the authority to make healthcare decisions for…
hCRFA substance being studied in the treatment of brain cancer. It is made naturally by the hypothalamus (a part of the brain) and can also be made in the…
HDACAn enzyme that changes the way histone binds to DNA. HDAC inhibitors are being studied as a treatment for cancer. Also called histone deacetylase.
HDAC inhibitor(...in-HIH-bih-ter) A substance that causes a chemical change that stops tumor cells from dividing.
HDRAn amount of radiation that is greater than that given in typical radiation therapy.
head and neck cancerCancer that arises in the head or neck region (in the nasal cavity, sinuses, lips, mouth, salivary glands, throat, or larynx [voice box]).
healing touchA form of complementary and alternative medicine based on the belief that a vital energy flows through the human body.
healthcare proxyA type of advance directive that gives a person (such as a relative, lawyer, or friend) the authority to make healthcare decisions for another person.
healthy controlIn a clinical study, a person who does not have the disorder or disease being studied.
heart cancer(hart KAN-ser) A rare cancer that develops in tissues of the heart. Also called cardiac sarcoma.
heat shock protein(... PROH-teen) One of a group of proteins that help protect cells from stresses such as heat, cold, and low amounts of oxygen or glucose (sugar).
Hedyotis diffusaAn herb used in traditional Chinese medicine to treat certain medical problems.
helical computed tomography(HEH-lih-kul kum-PYOO-ted toh-MAH-gruh-fee) A detailed picture of areas inside the body.
Helicobacter pylori(HEEL-ih-koh-BAK-ter py-LOR-ee) A type of bacterium that causes inflammation and ulcers in the stomach or small intestine.
helper T cellA type of white blood cell that helps stimulate immune system reactions. Helper T cells help activate cytotoxic T cells and macrophages by secreting…
hemagglutinin-neuraminidaseA protein found in the outer coat of paramyxoviruses. This protein helps virus particles bind to cells, making infection easier.
hemangiopericytoma(heh-MAN-jee-oh-PAYR-ih-sy-TOH-muh) A type of cancer involving blood vessels and soft tissue.
hemangiosarcomaA type of cancer that begins in the cells that line blood vessels.
hematogenous(HEE-muh-TAH-jeh-nus) Originating in the blood or spread through the bloodstream.
hematologic cancer(HEE-muh-tuh-LAH-jik KAN-ser) A cancer of the blood or bone marrow, such as leukemia or lymphoma.
Hematologist(HEE-muh-TAH-loh-jist) A doctor who specializes in treating blood disorders.
hematoma(HEE-muh-TOH-muh) A pool of clotted or partially clotted blood in an organ, tissue, or body space, usually caused by a broken blood vessel.
Hematopoiesis(hee-MA-toh-poy-EE-sus) The formation of new blood cells.
hematopoietic growth factor(hee-MA-toh-poy-EH-tik ...) A group of proteins that causes blood cells to grow and mature.
hematopoietic tissue(hee-MA-toh-poy-EH-tik TIH-shoo) Tissue in which new blood cells are formed.
hematoporphyrin derivative(HEE-muh-toh-POR-fih-rin deh-RIH-vuh-tiv) A drug used in photodynamic therapy that is absorbed by tumor cells.
heme (heem)The part of certain molecules that contains iron. The heme part of hemoglobin is the substance inside red blood cells that binds to oxygen in the lungs…
hemihypertrophy(HEM-ee-hy-PER-troh-fee) A condition in which one side of the body or a part of one side is larger than the other.
hemilaryngectomy(HEM-ee-LA-rin-JEK-toh-mee) An operation to remove one side of the larynx (voicebox).
hemochromatosis(HEE-moh-kroh-muh-TOH-sis) A condition in which the body absorbs more iron from food than it needs.
hemoglobin(HEE-moh-GLOH-bin) The substance inside red blood cells that binds to oxygen in the lungs and carries it to the tissues.
hemophagocytic lymphohistiocytosis(HEE-moh-FAG-oh-SIT-ik LIM-foh-HIS-tee-oh-sy-TOH-sis) A rare disorder in which histiocytes and lymphocytes (types of white blood cells) build up in organs…
hemophiliaGroup of hereditary disorders in which affected individuals fail to make enough of certain proteins needed to form blood clots.
hemoptysis(hee-MOP-tih-sis) Coughing or spitting up blood from the respiratory tract.
hemorrhageIn 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.
hemorrhoid(HEH-muh-ROYD) An enlarged or swollen blood vessel, usually located near the anus or the rectum.
heparin(HEH-puh-rin) 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…
hepatectomy(HEH-puh-TEK-toh-mee) Surgery to remove all or part of the liver.
hepatic arterial infusion(heh-PA-tik ar-TEER-ee-ul in-FYOO-zhun) A procedure to deliver chemotherapy directly to the liver.
hepatic arterial occlusion(heh-PA-tik ar-TEER-ee-ul uh-KLOO-zhun) A block in blood flow to the liver. It can happen while giving chemotherapy through a catheter in the hepatic…
hepatic artery(hih-PA-tik AR-tuh-ree) The major blood vessel that carries blood to the liver.
hepatic portal veinA blood vessel that carries blood to the liver from the stomach, small and large intestines, spleen, pancreas, and gallbladder. Also called portal vein.
hepatic veno-occlusive diseaseA condition in which some of the veins in the liver are blocked. It is sometimes a complication of high-dose chemotherapy given before a bone marrow…
hepatitis(HEH-puh-TY-tis) Disease of the liver causing inflammation. Symptoms include an enlarged liver, fever, nausea, vomiting, abdominal pain, and dark urine.
hepatitis A vaccine(HEH-puh-TY-tis ... vak-SEEN) A vaccine used to prevent infection with the hepatitis A virus, which causes a serious liver disease.
hepatitis A virus(HEH-puh-TY-tis ... VY-rus) A virus that causes a serious liver disease. It is usually spread by contact with an infected person's stool by eating food he…
hepatitis B virus(HEH-puh-TY-tis ... VY-rus) A virus that causes hepatitis (inflammation of the liver). It is carried and passed to others through blood or sexual contact.
hepatitis C virus(HEH-puh-TY-tis ... VY-rus) A virus that causes hepatitis (inflammation of the liver). It is carried and passed to others through blood or sexual contact.
hepatitis D virus(HEH-puh-TY-tis ⦠VY-rus) A type of hepatitis virus that may be present in the body at the same time as the hepatitis B virus.
hepatitis delta virus(HEH-puh-TY-tis DEL-tuh VY-rus) A type of hepatitis virus that may be present in the body at the same time as the hepatitis B virus.
hepatitis E virus(HEH-puh-TY-tis ⦠VY-rus) A virus that causes hepatitis (inflammation of the liver).
hepatitis G virus(HEH-puh-TY-tis ⦠VY-rus) A virus that may be found in patients with hepatitis (inflammation of the liver).
hepatobiliaryHaving to do with the liver, bile ducts, and/or gallbladder.
hepatoblastoma(HEP-a-toh-blas-TOH-muh) A type of liver tumor that occurs in infants and children.
hepatocellular carcinoma(HEP-a-toe-SEL-yoo-ler KAR-sih-NOH-muh) A type of adenocarcinoma, the most common type of liver tumor.
herbal medicine(ER-bul MEH-dih-sin) A type of medicine that uses roots, stems, leaves, flowers, or seeds of plants to improve health, prevent disease, and treat illness.
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.
hereditary mutation(huh-REH-dih-TAYR-ee myoo-TAY-shun) A gene change in a body's reproductive cell (egg or sperm) that becomes incorporated into the DNA of every cell in the…
hereditary nonpolyposis colon cancer(huh-REH-dih-TAYR-ee NON-PAH-lee-POH-sis KOH-lun KAN-ser) An inherited disorder in which affected individuals have a higher-than-normal chance of…
herpesvirus(HER-peez-VY-rus) A member of the herpes family of viruses.
heterocyclic amine(HEH-tuh-roh-SY-klik A-meen) A chemical that is formed when meat, poultry, or fish is cooked at high temperatures, such as frying, broiling, and…
heterogeneousMade up of elements or ingredients that are not alike.
heterogenic(het-er-o-JEN-ik) Derived from a different source or species. Also called heterogenous.
heterogenousDerived from a different source or species. Also called heterogenic.
hexyl 5-aminolevulinateA substance that is used to find and kill tumor cells. It enters tumor cells and becomes activated when exposed to a special type of light.
HHV8A type of herpesvirus that may cause Kaposi sarcoma (a rare cancer that can cause skin lesions) and a type of lymphoma (cancer that begins in the lymph…
HIFUA procedure in which high-energy sound waves are aimed directly at an area of abnormal cells or tissue in the body.