Cancer Dictionary – M
macrophage A type of white blood cell that surrounds and kills microorganisms, removes dead cells, and stimulates the action of other immune system cells.
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. Magnetic resonance imaging makes better images of organs and soft tissue than other scanning techniques, such as computed tomography (CT) or x-ray. Magnetic resonance imaging is especially useful for imaging the brain, the spine, the soft tissue of joints, and the inside of bones. Also called MRI, nuclear magnetic resonance imaging, and NMRI.
magnetic resonance perfusion imaging A special type of magnetic resonance imaging (MRI) that uses an injected dye in order to see blood flow through tissues. Also called perfusion magnetic resonance imaging.
malignancy A cancerous tumor that can invade and destroy nearby tissue and spread to other parts of the body.
malignant (muh-LIG-nunt) Cancerous. Malignant tumors can invade and destroy nearby tissue and spread to other parts of the body.
malignant mesothelioma (muh-LIG-nunt meh-zuh-thee-lee-OH-muh) A rare type of cancer in which malignant cells are found in the sac lining the chest or abdomen. Exposure to airborne asbestos particles increases one’s risk of developing malignant mesotheliomaMesothelium
malignant pleural effusion (muh-LIG-nunt PLOOR-ul eh-FYOO-zhun) condition in which cancer causes an abnormal amount of fluid to collect between the thin layers of tissue (pleura) lining the outside of the lung and the wall of the chest cavity. Lung cancer, breast cancer, lymphoma, and leukemia cause most malignant pleural effusions.
mediastinal pleura The thin membrane that lines the chest cavity in the area between the lungs.
mediastinoscope (MEE-dee-uh-STIN-oh-skope) 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 (MEE-dee-as-tih-NOS-koh-pee) 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 (mee-dee-a-STYE-num) The area between the lungs. The organs in this area include the heart and its large blood vessels, the trachea, the esophagus, the bronchi, and lymph nodes.
medical oncologist (MEH-dih-kul on-KAH-loh-jist) A doctor who specializes in diagnosing and treating cancer using chemotherapy, hormonal therapy, and biological 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.
membrane A very thin layer of tissue that covers a surface.
mesenteric membrane The peritoneal membrane that attaches the intestines to the abdominal wall near the back.
mesothelin (mez-oh-THEE-lin) A protein found on the surface of certain types of normal cells and cancer cells. Mesothelin may help these cells stick together and send signals. A higher-than-normal amount of mesothelin is found on some cancer cells, including mesothelioma, pancreatic cancer, and ovarian cancer.
mesothelioma (meh-zuh-thee-lee-OH-muh) A malignant (cancerous) tumor affecting the lining of the chest or abdomen. Exposure to asbestos particles in the air leads to the development of malignant mesothelioma. Learn More About Mesothelioma
metastasectomy (meh-TAS-tuh-SEK-toh-mee) Surgery to remove one or more metastases (tumors formed from cells that have spread from the primary tumor). When all metastases are removed, it is called a complete metastasectomy.
metastasis (meh-TAS-tuh-sis) The spread of cancer from one part of the body to another. A tumor formed by cells that have spread is called a “metastatic tumor” or a “metastasis.” The metastatic tumor contains cells that are like those in the original (primary) tumor. The plural form of metastasis is metastases (meh-TAS-tuh-SEEZ).
metastasize (meh-TAS-tuh-size) 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 (meh-tuh-STA-tik) Having to do with metastasis, which is the spread of cancer from one part of the body to another.
metastatic cancer (meh-tuh-STA-tik KAN-ser) Cancer that has spread from the place in which it started to other parts of the body.
metasynchronous Occurring at nearly the same time.
micrometastasis (MY-kroh-meh-TAS-tuh-sis) Small numbers of cancer cells that have spread from the primary tumor to other parts of the body and are too few to be picked up in a screening or diagnostic test.
mitosis (my-TOH-sis) The process by which a single parent cell divides to make two new daughter cells. Each daughter cell receives a complete set of chromosomes from the parent cell. This process allows the body to grow and replace cells.
mitotane (MY-toh-tane) An anticancer drug used in treating adrenocortical cancer and ACTH-producing pituitary tumors (Cushing disease).
mitotic activity Having to do with the presence of dividing (proliferating) cells. Cancerous tissue generally has more mitotic activity than normal tissues.
mitotic index In a population of cells, the ratio of the number of cells undergoing mitosis (cell division) to the number of cells not undergoing mitosis.
mitotic inhibitor A type of drug that blocks cell growth by stopping mitosis (cell division). They are used to treat cancer. Also called antimitotic agent.
mucinous carcinoma (MYOO-sin-us KAR-sih-NOH-muh) A type of cancer that begins in cells that line certain internal organs and produce mucin (the main component of mucus).
mucosa (myoo-KOH-suh) 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.
mucous membrane (MYOO-kus…) 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).
multidisciplinary opinion A treatment planning approach in which a number of doctors who are experts in different specialties (disciplines) review and discuss the medical condition and treatment options of a patient. In cancer treatment, a multidisciplinary opinion may include that of a medical oncologist (who provides cancer treatment with drugs), a surgical oncologist (who provides cancer treatment with surgery), and a radiation oncologist (who provides cancer treatment with radiation). Also called a tumor board review.
myelodysplasia (MY-eh-loh-dis-PLAY-zhuh) Abnormal bone marrow cells that may lead to myelogenous leukemia. MDS. Known to be caused by exposure to benzene.
myelodysplastic syndromes (MY-eh-loh-dis-PLAS-tik SIN-dromz) A group of diseases in which the bone marrow does not make enough healthy blood cells. Also called preleukemia and smoldering leukemia. . MDS. Known to be caused by exposure to benzene.
MDS A group of diseases in which the bone marrow does not make enough healthy blood cells. Also called preleukemia and smoldering leukemia. . Known to be caused by exposure to benzene.
myeloid (MY-eh-loyd) Having to do with or resembling the bone marrow. May also refer to certain types of hematopoietic (blood-forming) cells found in the bone marrow. Sometimes used as a synonym for myelogenous; for example, acute myeloid leukemia and acute myelogenous leukemia are the same disease.
myelomonocyte (MY-eh-loh-MON-oh-site) An abnormal type of white blood cell that is found in chronic myelomonocytic leukemia. These cells are similar to both monocytes and myelocytes (immature cells that develop into different types of immune system cells).
myeloproliferative disorder (MY-eh-loh-pruh-LIH-feh-RUH-tiv dis-OR-der) A group of slow growing blood cancers, including chronic myelogenous leukemia, in which large numbers of abnormal red blood cells, white blood cells, or platelets grow and spread in the bone marrow and the peripheral blood.