Glossary — C

CA-125 is a protein that can be measured in the blood. Higher levels are sometimes linked with ovarian cancer, but many ordinary conditions can raise it too. Because of that, the test is used as one piece of information among many, often to monitor a known condition rather than to screen healthy women.

Calcifications are small deposits of calcium that form in breast tissue and appear as bright white flecks on a mammogram. Most are completely harmless and very common, especially as you get older. Occasionally their size, shape, or pattern prompts a closer look to make sure nothing concerning is developing.

Calcium is a mineral your body needs to build and maintain strong bones and teeth. It also plays a role in how muscles contract, how nerves send signals, and how blood clots. When you do not get enough, your body draws calcium from your bones, which over time can leave them weaker.

Carcinoma is a type of cancer that starts in epithelial cells, the cells that line the skin, organs, and internal passages of the body. Most breast, cervical, lung, and colon cancers are carcinomas. The word describes where the cancer begins rather than how serious it is, which depends on many other factors.

The carpal tunnel is a narrow channel in the wrist through which a major nerve and several tendons pass. When the tunnel narrows or the tissues swell, the nerve gets squeezed, leading to numbness, tingling, weakness, or pain in the hand and fingers, a condition known as carpal tunnel syndrome.

A catheter is a thin, flexible tube that can be guided into a blood vessel, the bladder, or another part of the body. Depending on its purpose, it can deliver medicine or contrast dye, drain fluid, or carry tiny instruments to a precise location, often without the need for major surgery.

Cervical cancer develops in the cells of the cervix, the narrow lower end of the uterus that opens into the vagina. It is most often caused by long-lasting infection with certain types of human papillomavirus. Because it usually develops slowly from detectable changes, regular screening makes it one of the most preventable cancers.

Chemoprevention is the use of medicines to reduce the risk of developing cancer in the first place, rather than to treat cancer that already exists. For breast cancer, certain drugs that block estrogen's effects may lower risk in women who face a higher-than-average chance of the disease.

Chemotherapy uses powerful medicines to kill cancer cells or stop them from dividing. Because the drugs travel through the bloodstream, they can reach cancer cells throughout the body. This makes chemotherapy useful when there is a chance cancer cells have spread beyond the original site, and it is often combined with other treatments.

Cholesterol is a waxy, fat-like substance found in your blood and every cell of your body. You need some of it to build cells and make hormones. But when there is too much of certain types, it can build up in artery walls, narrowing them and raising the risk of heart disease and stroke.

A clinical breast exam is a physical examination of the breasts and underarm area performed by a trained health professional. Using their hands and eyes, they check for lumps, changes in shape or skin, and other findings, complementing what you notice yourself and what a mammogram can reveal.

A clinical trial is a research study in which people volunteer to help test a new treatment, screening method, or way of managing a condition. Trials follow strict rules to measure whether something is safe and effective, and they are how nearly every treatment in use today was proven to work.

Colposcopy is a procedure in which a doctor uses a lighted magnifying instrument to examine the cervix, vagina, and vulva closely. It is often done after a Pap smear or HPV test shows changes, so any abnormal-looking areas can be seen clearly and, if needed, sampled for further testing.

Contralateral simply means "on the other side." In breast health, it often refers to the breast opposite the one affected by a condition, such as the contralateral breast when cancer has been found on one side. It is a precise way for your care team to describe location.

A contrast agent is a substance given before or during an imaging test that makes specific organs, blood vessels, or tissues stand out more clearly. By temporarily changing how an area absorbs X-rays or responds to magnetic fields, it helps radiologists see details that might otherwise be hard to make out.

A core needle biopsy uses a hollow needle to remove one or more small cylinders, or cores, of tissue from an area of concern. The samples are larger than those from a fine needle, giving the laboratory enough tissue to determine whether the area is benign or needs further attention.

A CT scan, short for computed tomography, takes a series of X-ray images from many angles and uses a computer to combine them into detailed cross-sectional pictures. These "slices" let your care team see bones, organs, blood vessels, and soft tissues with far more detail than a single X-ray can provide.

A cyst is a closed, sac-like pocket of tissue that is usually filled with fluid. Cysts are very common in the breast, especially before menopause, and the great majority are benign. They can sometimes be felt as a smooth, movable lump and are easily identified with imaging such as ultrasound.