Glossary — P

A Pap smear — also called a Pap test — is a screening procedure in which a small sample of cells is collected from the cervix and examined under a microscope for abnormalities. It is one of the most effective cancer-prevention tools available, capable of detecting precancerous changes years before cervical cancer would develop.

Pathology is the branch of medicine concerned with the study and diagnosis of disease through laboratory analysis. When a biopsy or surgical specimen is sent to the pathology lab, a specialist called a pathologist examines it microscopically to determine whether cells are normal, precancerous, or malignant, and to characterize what type of cancer is present.

Polycystic ovary syndrome (PCOS) is one of the most common hormonal disorders in women of reproductive age, affecting an estimated 1 in 10. It involves an imbalance of reproductive hormones that can disrupt ovulation, cause irregular periods, raise androgen (male hormone) levels, and produce small follicle cysts on the ovaries. PCOS also carries links to insulin resistance and long-term metabolic health.

Perimenopause is the years-long transition before menopause during which the ovaries gradually produce less estrogen and progesterone. Periods may become irregular, and many women experience symptoms such as hot flashes, sleep disruption, mood changes, and vaginal dryness. It typically begins in the mid-40s but can start earlier.

A PET (positron emission tomography) scan is a type of nuclear medicine imaging that maps metabolic activity in the body. By injecting a small amount of radioactive glucose into the bloodstream, the scan reveals which tissues are consuming energy at higher rates — a hallmark of cancer cells, which tend to use glucose more aggressively than normal tissue.

In cardiovascular medicine, plaque refers to deposits that accumulate inside artery walls, composed of cholesterol, fatty substances, calcium, and cellular waste. As plaque builds up, it narrows and hardens the arteries — a process called atherosclerosis — which can reduce blood flow to the heart, brain, and other organs and raise the risk of heart attack and stroke.

A Port-a-Cath (or implanted port) is a small medical device placed surgically under the skin of the chest, connected to a large vein. It allows medications like chemotherapy, fluids, and blood products to be delivered directly into the bloodstream through a simple needle stick into the port, sparing peripheral veins from repeated punctures.

Progesterone is a steroid hormone produced primarily by the ovaries after ovulation. It prepares the lining of the uterus (endometrium) to receive a fertilized egg and, if pregnancy occurs, helps maintain it in the early stages. Progesterone levels rise and fall throughout the menstrual cycle and decline significantly during perimenopause and menopause.

A progesterone receptor (PR) is a protein found inside certain cells that binds to the hormone progesterone and triggers a cellular response. In breast cancer, testing whether tumor cells carry progesterone receptors — reported as PR-positive (PR+) or PR-negative (PR−) — is a standard part of diagnosis that helps determine which treatments are most likely to be effective.

Prolactin is a hormone released by the pituitary gland at the base of the brain. It is best known for triggering and sustaining milk production after childbirth, but it also plays a role in regulating the menstrual cycle. Abnormally high prolactin levels (hyperprolactinemia) can disrupt ovulation, cause irregular or absent periods, and sometimes lead to nipple discharge in people who are not breastfeeding.

A prophylactic mastectomy is the surgical removal of one or both breasts performed not to treat existing cancer, but to dramatically reduce the future risk of developing it. It is most often considered by women with high-risk BRCA gene mutations, a strong family history, or other factors that give them a significantly elevated lifetime breast cancer risk.

A pulmonary embolism occurs when a blood clot — most often formed in a deep leg vein — breaks free, travels through the bloodstream, and lodges in one of the arteries supplying the lungs. It is a medical emergency that requires prompt treatment to restore blood flow and oxygen delivery.