Medical terms A–Z

Removing more tissue does not by itself buy more survival, which is why breast-conserving surgery with radiation matches mastectomy for many early cancers.

Mastitis is breast tissue inflammation most common during breastfeeding, though its symptoms can occasionally overlap with those of a rare inflammatory breast cancer.

Rubbing one makes it swell, redden and itch within minutes, a response distinctive enough to identify the lesion without a biopsy.

A finding, condition, or trait labeled maternal originates from or relates to the mother, as distinguished from paternal or fetal factors.

Because these enzymes can also weaken normal tissue architecture, their activity is implicated in disease processes well beyond their role in ordinary repair.

One of a group of aggressive (fast-growing) non-Hodgkin lymphomas that begin in mature T lymphocytes (T cells that have matured in the thymus gland and gone to other lymphatic sites in the body…

A type of benign (not cancer) germ cell tumor (type of tumor that begins in the cells that give rise to sperm or eggs) that often contains several different types of tissue such as hair, muscle, and…

A substance being studied in the treatment of some types of cancer and other conditions.

The maxillary sinus is the largest paranasal sinus, an air filled space within the cheekbone that drains into the nasal cavity.

A test that measures the strength of the muscles used in breathing.

An abbreviation for a chemotherapy combination used with other types of therapy to treat colorectal cancer.

MBL is a condition marked by an elevated number of identical B cells in the blood that occasionally precedes a related blood cancer.

A protein found in skin and eye cells that make melanin (a pigment that gives color to the skin and helps protect it from damage by ultraviolet light).

A drug that belongs to a family of drugs called ribonucleotide reductase inhibitors.

A monoclonal antibody being studied in the treatment of certain types of cancer.

A monoclonal antibody that is being studied in the treatment of some lymphomas.

The familiar average, dependable when values cluster together and easily dragged off course when a few sit far out.

The average time that patients in a clinical study remained alive.

The virus that causes measles (a highly contagious disease marked by fever, cough, and raised red spots on the skin).

A tumor that can be accurately measured in size.

A monoclonal antibody that is being studied in the treatment of certain lymphoproliferative disorders and psoriasis.

A substance being studied in the treatment of some types of cancer and other conditions.

A lymph node located above the collar bone and between the center of the body and a line drawn through the nipple to the shoulder.

In statistics, the median is the middle value in an ordered data set, a measure clinicians often favor over the average when data are skewed.

The time from either diagnosis or treatment at which half of the patients with a given disease are found to be, or expected to be, still alive.

A fibrous cord that connects the urinary bladder to the umbilicus (navel).

The thin membrane that lines the chest cavity in the area between the lungs.

A thin, tube-like instrument used to examine the tissues and lymph nodes in the area between the lungs.

A short operation through a small cut above the breastbone, giving direct access to the lymph nodes lying around the windpipe.

Nothing in this compartment has room to expand, so a mass here tends to declare itself by pressing on whatever lies beside it.

Fifty separate programs under one name, which is why Medicaid enrollment alone says little about what a given person is covered for.

Refers to the use of drugs to suppress the function of the ovaries or testicles.

Regulatory oversight for medical devices generally scales with risk, so a simple bandage faces far less scrutiny than an implanted pacemaker.

A doctor who specializes in diagnosing and treating cancer using chemotherapy, hormonal therapy, biological therapy, and targeted therapy.

Age is the usual route in, but disability, kidney failure and ALS also qualify, and the parts cover different kinds of care.

From a swallowed tablet to a skin patch, the form is chosen to suit how the substance must travel to reach its target.

A field and a bottle share one word, and the branches of the field are themselves called medicine, as in internal or nuclear medicine.

A drug used to prevent endometrial cancer.

A rare type of breast cancer that often can be treated successfully.

The one thyroid cancer arising from a different cell type entirely, and the one most likely to run in families.

The most common cancerous brain tumor of childhood, growing where balance and coordination are controlled.

A machine that uses electricity to form a stream of fast-moving subatomic particles.

Megestrol is a synthetic progestin used to treat certain hormone sensitive cancers and to help stimulate appetite in people with significant weight loss.

The division that halves the chromosome count and shuffles the deck, so no two eggs or sperm carry the same combination.

A protein found on normal melanocytes (cells that make the pigment melanin) in the skin and in the retina.

Melanin is the pigment responsible for skin, hair, and eye color that also helps absorb and limit damage from ultraviolet light.

A protein found in skin and eye cells that make melanin (a pigment that gives color to the skin and helps protect it from damage by ultraviolet light).

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

Far less common than the everyday skin cancers but responsible for most deaths from them, because it spreads while it is still small.

The earliest recognized stage of melanoma, still trapped in the outer skin layer where no blood or lymph vessels reach.

A cancer vaccine prepared from human melanoma cancer cells.

A protein found in skin and eye cells that make melanin (a pigment that gives color to the skin and helps protect it from damage by ultraviolet light).

A membrane is a thin sheet of tissue that lines, covers, separates, or encloses a body structure or cavity.

An inherited condition that may result in the development of cancers of the endocrine system.

An anticancer drug that belongs to the family of drugs called antitumor antibiotics.

A rare, inherited disorder that affects the endocrine glands and can cause tumors in the parathyroid and pituitary glands and the pancreas.

Having to do with the meninges (three thin layers of tissue that cover and protect the brain and spinal cord).

One condition carrying at least five names, recognized by trouble that refuses to point to a single spot in the nervous system.

A serious problem that may occur in leukemia.

A serious problem that may occur in cancer in which cancer cells spread from the original (primary) tumor to the meninges (thin layers of tissue that cover and protect the brain and spinal cord).

A condition marked by headache, fever, and a stiff neck, which is caused when the meninges (three thin layers of tissue that cover and protect the brain and spinal cord) become irritated.

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

A type of slow-growing tumor that forms in the meninges (thin layers of tissue that cover and protect the brain and spinal cord).

Inflammation of the meninges (three thin layers of tissue that cover and protect the brain and spinal cord).

Hormones (estrogen, progesterone, or both) given to women after menopause to replace the hormones no longer produced by the ovaries.

Bleeding heavy enough to disrupt daily life often traces to fibroids, hormone shifts or an inherited clotting problem, and steadily drains iron.

The menstrual cycle is the recurring hormonal sequence that prepares the uterine lining for pregnancy and sheds it when pregnancy does not occur.

The periodic discharge of blood and tissue from the uterus.

Menstruation is the cyclical shedding of the uterine lining that occurs when pregnancy does not take place, recurring throughout the reproductive years.

A specialist who can talk with patients and their families about emotional and personal matters, and can help them make decisions.

A mint compound that persuades cold-sensing nerves to fire, producing a chill on skin whose temperature has not changed.

A drug being studied in the treatment of young adults with bone cancer that has gotten worse or come back.

Three chemical forms with three different hazards, which is why an exposure cannot be judged from the word mercury alone.

An easy or painless death, or the intentional ending of the life of a person suffering from an incurable or painful disease at his or her request.

A touch sensor that also behaves like a hormone releasing cell, and the namesake of a cancer it may not actually produce.

A rare type of cancer that forms on or just beneath the skin, usually in parts of the body that have been exposed to the sun.

Merkel cell carcinoma is a rare, aggressive skin cancer linked to sun exposure and immune suppression, arising from neuroendocrine skin cells.

Mesenchymal describes embryonic connective tissue and the cells derived from it that can develop into bone, cartilage, fat, and blood related tissue.

The peritoneal membrane that attaches the intestines to the abdominal wall near the back.

A rare type of tumor, usually of the female genital tract, in which the insides of the cells look clear when viewed under a microscope.

A surface protein the cells that make it barely seem to need, which is precisely what makes it a usable target on tumors.

A cancer of the mesothelium, the thin lining around the lungs, abdomen or heart, strongly associated with past asbestos exposure.

One copy can be read many times over before it is destroyed, which is how a single gene yields thousands of protein molecules.

One adjective covers energy use, inherited enzyme faults, acid balance and a cluster of risk factors, so context decides its meaning.

Metabolic acidosis is a drop in blood pH caused by excess acid production or loss of the body's bicarbonate buffer.

A condition in which normal metabolic processes are disrupted, usually because of a missing enzyme.

Metabolic syndrome describes a cluster of findings, including abdominal obesity and abnormal blood pressure, glucose, and cholesterol levels, that together raise cardiovascular and diabetes risk.

Metabolic syndrome X is an older name for metabolic syndrome, the clustering of abdominal obesity, high blood pressure, and abnormal glucose and lipid levels.

Treatment to correct changes in metabolism that can be caused by disease.

In alternative medicine, a theory that people fall into one of three groups (protein, carbohydrate, or mixed type) based on the main type of food that their bodies need to stay healthy.

Two opposing sets of reactions run at once, one tearing molecules apart for energy and the other spending that energy building new ones.

A substance made or used when the body breaks down food, drugs or chemicals, or its own tissue (for example, fat or muscle tissue).

A taste of coins or blood with nothing metal in the mouth, arising from the taste and smell pathways rather than the food.

Metaplasia is a reversible change in which one mature cell type is replaced by another, typically in response to ongoing irritation or stress.

A general term used to describe cancer that begins in cells that have changed into another cell type (for example, a squamous cell of the esophagus changing to resemble a cell of the stomach).

Surgery to remove one or more metastases (tumors formed from cells that have spread from the primary tumor).

A tumor in the liver made of colon cells is still colon cancer, which is why origin governs treatment rather than address.

A tumor found in the liver may still be breast cancer, because spreading cells keep the identity of where they began.

Metasynchronous describes a second finding, such as a related tumor, identified within a short interval of the first rather than at the same time.

Swelling of the abdomen caused by gas in the intestines or peritoneal cavity.