Glossary

Papule: A skin lesion that is small, solid, and raised.

Pathologist: A doctor who identifies diseases by studying cells and tissues under a microscope.

Pathology report: The description of cells and tissues made by a pathologist based on microscopic evidence, and sometimes used to make a diagnosis of a disease.

Perfusion: Bathing an organ or tissue with a fluid. In regional perfusion, a specific area of the body (usually an arm or a leg) receives high doses of anticancer drugs through a blood vessel. Such a procedure is performed to treat cancer that has not spread.

Peripheral: Away from the center. Refers to the areas away from the center of the body or body part. The hands are peripheral to the shoulder. The toes are peripheral to the knees.

Pigment: A substance that gives color to tissue. Pigments are responsible for the color of skin, eyes, and hair.

Platelet count: A test that measures the number of platelets in blood. Platelets are necessary for normal blood clotting (hemostasis). Most importantly, they aggregate (clump) together to plug small holes in damaged vessels. They also activate factor VIII (a component of the coagulation cascade) and release phospholipids necessary for the coagulation cascade.

Prognosis: A prediction of the probable course of the disease.

Protein: A molecule made up of amino acids that are needed for the body to function properly. Proteins are the basis of body structures such as skin and hair and of substances such as enzymes, cytokines, and antibodies.

Psoriasis: A chronic disease of the skin marked by red patches covered with white scales.

Psychiatrist: A medical doctor who specializes in the prevention, diagnosis, and treatment of mental, emotional, and behavioral disorders.

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