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Glossary - M


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  • Magnetic resonance imaging

    (mag-NEH-tik REH-zuh-nunts IH-muh-jing)

    A procedure in which radio waves and a powerful magnet linked to a computer are used to create detailed pictures of areas inside the body. These pictures can show the difference between normal and diseased tissue. MRI makes better images of organs and soft tissue than other scanning techniques, such as computed tomography (CT) or x-ray. MRI is especially useful for imaging the brain, the spine, the soft tissue of joints, and the inside of bones. Also called magnetic resonance imaging, NMRI, and nuclear magnetic resonance imaging.

  • Malignant


    A term used to describe cancer. Malignant cells grow in an uncontrolled way and can invade nearby tissues and spread to other parts of the body through the blood and lymph system.

  • Malignant tumor

    A mass of cancer cells that may invade surrounding tissues or spread (metastasize) to distant areas of your body.

  • Malnutrition


    A condition caused by not getting enough calories or the right amount of key nutrients, such as vitamins and minerals, that are needed for health. Malnutrition may occur when there is a lack of nutrients in the diet or when the body cannot absorb nutrients from food. Cancer and cancer treatment may cause malnutrition.

  • Mammogram


    An x-ray of the breast.

  • Manual healing

    (MAN-yoo-ul HEE-ling)

    A type of therapy in which the therapist moves or manipulates one or more parts of the patients body. It may be used to treat pain, stress, anxiety, and depression, and for general well-being. Examples include chiropractic treatments, physical therapy, and massage therapy. Also called manipulative and body-based practice and physical touch methods.

  • Marker


    A diagnostic indication that disease may develop.

  • Markers


    Diagnostic indications that disease may develop.

  • Mass


    In medicine, a lump in the body. It may be caused by the abnormal growth of cells, a cyst, hormonal changes, or an immune reaction. A mass may be benign (not cancer) or malignant (cancer).

  • Mast cell

    (mast sel)

    A type of white blood cell.

  • Mean survival

    (meen ser-VY-vul)

    The average length of time from either the date of diagnosis or the start of treatment for a disease, such as cancer, that patients diagnosed with the disease are still alive. In a clinical trial, measuring mean survival is one way to see how well a new treatment works.

  • Measurable disease

    (MEH-zur-uh-bul dih-ZEEZ)

    A tumor that can be accurately measured in size. This information can be used to judge response to treatment.

  • Median survival

    (MEE-dee-un ser-VY-vul)

    The length of time from either the date of diagnosis or the start of treatment for a disease, such as cancer, that half of the patients in a group of patients diagnosed with the disease are still alive. In a clinical trial, measuring the median survival is one way to see how well a new treatment works. Also called median overall survival.

  • Mediastinoscope


    A thin, tube-like instrument used to examine the tissues and lymph nodes in the area between the lungs. These tissues include the heart and its large blood vessels, trachea, esophagus, and bronchi. The mediastinoscope has a light and a lens for viewing and may also have a tool to remove tissue. It is inserted into the chest through a cut above the breastbone.

  • Mediastinoscopy


    A procedure in which a mediastinoscope is used to examine the organs in the area between the lungs and nearby lymph nodes. A mediastinoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove tissue to be checked under a microscope for signs of disease. The mediastinoscope is inserted into the chest through an incision above the breastbone. This procedure is usually done to get a tissue sample from the lymph nodes on the right side of the chest.

  • Mediastinum


    The area between the lungs. The organs in this area include the heart and its large blood vessels, the trachea, the esophagus, the thymus, and lymph nodes but not the lungs.

  • Medical history

    MEH-dih-kul HIH-stuh-ree

    A record of information about a persons health. A personal medical 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 medical history includes health information about a person's close family members (parents, grandparents, children, brothers, and sisters). This includes their current and past illnesses. A family medical history may show a pattern of certain diseases in a family.

  • Medical oncologist

    (MEH-dih-kul on-KAH-loh-jist)

    A doctor who has special training in diagnosing and treating cancer using chemotherapy, hormonal therapy, biological therapy, and targeted therapy. A medical oncologist often is the main health care provider for someone who has cancer. A medical oncologist also gives supportive care and may coordinate treatment given by other specialists.

  • Medication


    A legal drug that is used to prevent, treat, or relieve symptoms of a disease or abnormal condition.

  • Medicine


    A substance used in treating disease.

  • Medulloblastoma


    A malignant brain tumor that begins in the lower part of the brain and that can spread to the spine or to other parts of the body. Medulloblastomas are a type of primitive neuroectodermal tumor (PNET).

  • Melanocytes


    A cell in the skin and eyes that produces and contains the pigment called melanin.

  • Melanoma


    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 chances for a cure are much less.

  • Melatonin


    A hormone made by the pineal gland (tiny organ near the center of the brain). Melatonin helps control the bodys sleep cycle, and is an antioxidant. It is also made in the laboratory and sold as a supplement.

  • MEN syndrome

    ... SIN-drome

    An inherited condition that may result in the development of cancers of the endocrine system. There are several types of MEN syndrome, and patients with each type may develop different types of cancer. The altered genes that cause each type can be detected with a blood test. Also called multiple endocrine neoplasia syndrome.

  • Meningeal leukemia

    (meh-NIN-jee-ul loo-KEE-mee-uh)

    A serious problem that may occur in leukemia. In meningeal leukemia, cancer cells have spread from the original (primary) tumor to the meninges (thin layers of tissue that cover and protect the brain and spinal cord). The cancer may cause the meninges to be inflamed. Also called leukemic leptomeningitis and leukemic meningitis.

  • Meninges


    The three thin layers of tissue that cover and protect the brain and spinal cord.

  • Meningitis


    An infection of the membranes and fluid around the brain and spinal cord.

  • Menopause


    The time of life when a womans ovaries stop producing hormones and menstrual periods stop. Natural menopause usually occurs around age 50. A woman is said to be in menopause when she hasnt had a period for 12 months in a row. Symptoms of menopause include hot flashes, mood swings, night sweats, vaginal dryness, trouble concentrating, and infertility.

  • Menstrual periods

    (MEN-stroo-ul PEER-ee-uds)

    The periodic discharge of blood and tissue from the uterus. From puberty until menopause, menstruation occurs about every 28 days, but does not occur during pregnancy.

  • Menstruation


    Periodic discharge of blood and tissue from the uterus. From puberty until menopause, menstruation occurs about every 28 days when a woman is not pregnant.

  • Mercaptopurine


    A drug used with other drugs to treat acute lymphoblastic leukemia. It is also being studied in the treatment of other types of cancer. Mercaptopurine stops cells from making DNA and may kill cancer cells. It is a type of antimetabolite. Also called Purinethol and Purixan.

  • Metabolic


    Having to do with metabolism (the total of all chemical changes that take place in a cell or an organism to produce energy and basic materials needed for important life processes).

  • Metabolic syndrome

    MEH-tuh-BAH-lik SIN-drome

    A condition marked by extra fat around the abdomen, high levels of blood glucose (sugar) when not eating, high levels of triglycerides (a type of fat) in the blood, low levels of high-density lipoproteins (a type of protein that carries fats) in the blood, and high blood pressure. People with metabolic syndrome are at increased risk of diabetes mellitus and diseases of the heart and blood vessels. Also called metabolic syndrome X.

  • Metabolism


    The chemical changes that take place in a cell or an organism. These changes make energy and the materials cells and organisms need to grow, reproduce, and stay healthy. Metabolism also helps get rid of toxic substances.

  • Metastasis

    The spread of cancer cells from the place where they first formed to another part of the body. In metastasis, cancer cells break away from the original (primary) tumor, travel through the blood or lymph system, and form a new tumor in other organs or tissues of the body. The new, metastatic tumor is the same type of cancer as the primary tumor. For example, if breast cancer spreads to the lung, the cancer cells in the lung are breast cancer cells, not lung cancer cells.

  • Metastasize


    To spread from one part of the body to another. When cancer cells metastasize and form secondary tumors, the cells in the metastatic tumor are like those in the original (primary) tumor.

  • Metastatic


    Having to do with metastasis, which is the spread of cancer from the primary site (place where it started) to other places in the body.

  • Methodology


    In medicine, the rules and procedures for doing research and evaluating results.

  • Methotrexate


    A drug used to treat many types of cancer. It is also used to treat rheumatoid arthritis and severe psoriasis (a type of skin condition). Methotrexate stops cells from using folic acid to make DNA and may kill cancer cells. It may also lower the bodys immune response. Methotrexate is a type of antimetabolite and a type of antifolate. Also called amethopterin, MTX, Rheumatrex, and Trexall.

  • Methylprednisolone


    A corticosteroid hormone replacement.

  • Microorganism


    An organism that can be seen only through a microscope. Microorganisms include bacteria, protozoa, algae, and fungi. Although viruses are not considered living organisms, they are sometimes classified as microorganisms.

  • Minimal Residual Disease

    (MIH-nih-mul ree-ZID-yoo-ul dih-ZEEZ)

    A term used to describe a very small number of cancer cells that remain in the body during or after treatment. Minimal residual disease can be found only by highly sensitive laboratory methods that are able to find one cancer cell among one million normal cells. Checking to see if there is minimal residual disease may help plan treatment, find out how well treatment is working or if cancer has come back, or make a prognosis. Minimal residual disease testing is used mostly for blood cancers such as lymphoma and leukemia. Also called MRD.

  • Minimally invasive surgery

    (MIH-nih-muh-lee in-VAY-siv SER-juh-ree)

    Surgery that is done using small incisions (cuts) and few stitches. During minimally invasive surgery, one or more small incisions may be made in the body. A laparoscope (thin, tube-like instrument with a light and a lens for viewing) is inserted through one opening to guide the surgery. Tiny surgical instruments are inserted through other openings to do the surgery. Minimally invasive surgery may cause less pain, scarring, and damage to healthy tissue, and the patient may have a faster recovery than with traditional surgery.

  • Mitigate


    To make milder or less painful.

  • Mitochondria


    Small structures in a cell that are found in the cytoplasm (fluid that surrounds the cell nucleus). Mitochondria make most of the energy for the cell and have their own genetic material that is different from the genetic material found in the nucleus. Many diseases are caused by mutations (changes) in the DNA of mitochondria. Mitochondria are cell organelles.

  • Mitotane


    An anticancer drug used in treating adrenocortical cancer and ACTH-producing pituitary tumors (Cushing disease).

  • Mixed lymphocyte culture assay

    A technique to determine compatibility between individuals. Differences in HL-A antigens between two individuals will cause an immune reaction between their lymphocytes mixed in culture. This reactivity can be measured in the MLC assay. Compatible individuals have negative MLC's.

  • Modality


    A method of treatment. For example, surgery and chemotherapy are treatment modalities.

  • Moderate sedation

    (MAH-deh-rut seh-DAY-shun)

    A level of sedation in which a person is asleep but wakes when spoken to or touched. Moderate sedation is caused by special drugs and is used to help relieve anxiety during certain medical or surgical procedures. Drugs that relieve pain may be given at the same time. Also called conscious sedation.

  • Molecular marker

    (muh-LEH-kyoo-ler MAR-ker)

    A biological molecule found in blood, other body fluids, or tissues that is a sign of a normal or abnormal process, or of a condition or disease. A molecular marker may be used to see how well the body responds to a treatment for a disease or condition. Also called biomarker and signature molecule.

  • Monitor


    A machine that continually records your heart activity.

  • Monoclonal antibodies

    Antibodies made in the laboratory and designed to target specific substances called antigens. Monoclonal antibodies which have been attached to chemotherapy drugs or radioactive substances are being studied to see if they can seek out antigens unique to cancer cells and deliver these treatments directly to the cancer, thus killing the cancer cells without harming healthy tissue. Monoclonal antibodies are also used in other ways, for example, to help find and classify cancer cells.

  • Monoclonal Antibody

    (MAH-noh-KLOH-nul AN-tee-BAH-dee)

    A type of protein made in the laboratory that can bind to substances in the body, including cancer cells. There are many kinds of monoclonal antibodies. A monoclonal antibody is made so that it binds to only one substance. Monoclonal antibodies are being used to treat some types of cancer. They can be used alone or to carry drugs, toxins, or radioactive substances directly to cancer cells.

  • Monocyte


    A type of immune cell that is made in the bone marrow and travels through the blood to tissues in the body where it becomes a macrophage or a dendritic cell. Macrophages surround and kill microorganisms, ingest foreign material, remove dead cells, and boost immune responses. During inflammation, dendritic cells boost immune responses by showing antigens on their surface to other cells of the immune system. A monocyte is a type of white blood cell and a type of phagocyte.

  • mTOR inhibitor

    (… in-HIH-bih-ter)

    A substance that blocks a protein called mTOR, which helps control cell division. Blocking mTORs action may keep cancer cells from growing and prevent the growth of new blood vessels that tumors need to grow. Some mTOR inhibitors are used to treat cancer.

  • Mucosa


    The moist, inner lining of some organs and body cavities (such as the nose, mouth, lungs, and stomach). Glands in the mucosa make mucus (a thick, slippery fluid). Also called mucous membrane.

  • Mucositis


    Inflammation of the mucous membrane, e.g. Inside the mouth.

  • Mucous membrane

    (MYOO-kus MEM-brayn)

    The moist, inner lining of some organs and body cavities (such as the nose, mouth, lungs, and stomach). Glands in the mucous membrane make mucus (a thick, slippery fluid). Also called mucosa.

  • Multidisciplinary


    In medicine, a term used to describe a treatment planning approach or team that includes a number of doctors and other health care professionals who are experts in different specialties (disciplines). In cancer treatment, the primary disciplines are medical oncology (treatment with drugs), surgical oncology (treatment with surgery), and radiation oncology (treatment with radiation).

  • Multidrug resistance

    (MUL-tee-... reh-ZIH-stunts)

    Adaptation of tumor cells to anticancer drugs in ways that make the drugs less effective.

  • Multigene test

    (MUL-tee-jeen ...)

    A laboratory test in which many genes are studied in a sample of tissue. Multigene tests may help find mutations (changes) in certain genes that may increase a persons risk of a disease such as cancer. They may also look at the activity of certain genes in a sample of tissue. Multigene tests may be used to help plan treatment or make a prognosis, including helping to predict whether cancer will spread to other parts of the body or come back. Also called multiple-gene panel test and multiple-gene test.

  • Musculoskeletal


    Having to do with muscles, bones, tendons, ligaments, joints, and cartilage.

  • Mutate


    To change the genetic material of a cell. The changes (mutations) can be harmful, beneficial, or have no effect.

  • Mutation


    Any change in the DNA sequence of a cell. Mutations may be caused by mistakes during cell division, or they may be caused by exposure to DNA-damaging agents in the environment. Mutations can be harmful, beneficial, or have no effect. If they occur in cells that make eggs or sperm, they can be inherited; if mutations occur in other types of cells, they are not inherited. Certain mutations may lead to cancer or other diseases.

  • MYCN gene

    (... jeen)

    MYCN is important for cell growth. Having more than 10 copies of the gene is called MYCN amplification. Neuroblastoma with MYCN amplification is more likely to spread in the body and less likely to respond to treatment.

  • Myelin


    The fatty substance that covers and protects nerves.

  • Myelodysplastic Syndrome

    (MY-eh-loh-dis-PLAS-tik SIN-drome)

    A type of cancer in which the bone marrow does not make enough healthy blood cells (white blood cells, red blood cells, and platelets) and there are abnormal cells in the blood and/or bone marrow. When there are fewer healthy blood cells, infection, anemia, or bleeding may occur. Sometimes, myelodysplastic syndrome becomes acute myeloid leukemia (AML). Also called MDS.

  • Myelosuppression


    A condition in which bone marrow activity is decreased, resulting in fewer red blood cells, white blood cells, and platelets. Myelosuppression is a side effect of some cancer treatments. When myelosuppression is severe, it is called myeloablation.