Palliative Treatment: Treatment that does not alter the course of a disease, but improves the quality of life by relieving symptoms, such as pain.

Palpation: A technique in which a doctor presses on the surface of the body to feel the organs or tissues underneath. A palpable mass is one that can be felt.

Pancytopenia: A condition where there is a reduction in red blood cells, white blood cells and platelets.

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

PBSC: See Peripheral Blood Stem Cells

Pelvis: Also called pelvic area. The skeleton of the lower part of the abdomen, located between the hip bones.

Peripheral Blood Stem Cells: The cells originating in the bone marrow from which all blood cells develop. These cells may divide to form more stem cells or mature into a variety of different blood cells. The stem cells may be collected from the blood system through a procedure called apheresis.

Peripheral Blood Stem Cell (PBSC) Donation: Hematopoietic stem cells are collected from a donor's circulating blood through an apheresis procedure following mobilization from the marrow with Filgrastim. The stem cells are then transplanted into a recipient.

Petechiae: Small areas of bleeding that appear on the skin. This can be due to low platelet counts.

Pheresis: See Apheresis

Phlebotomy: Withdrawing blood from a vein (usually a vein in the arm) or an intravenous catheter for testing purposes.

Placebo: An inactive substance ("sugar pill") used in research, to compare the effects of a given treatment against no treatment.

Plasma: The liquid portion of unclotted blood. (Serum is the liquid portion of clotted blood.)

Plasmapheresis: Blood is taken from a vein and circulates through a machine, which separates the cells and the plasma. The plasma is removed and replaced with a substitute, which is returned to the body along with the blood cells.

Platelet: A blood cell that assists in blood clotting. Also called thrombocytes. Patients are at risk to bleed excessively from surgery or trauma if the platelet count is less than 50,000. An increased risk of spontaneous bleeding occurs with platelet counts less than 20,000.

Platelet Count: The number of platelets in a blood sample.

Pleura: The thin transparent membrane that lines the chest wall and doubles back to cover the lungs, thereby forming a continuous sac enclosing the narrow pleural cavity. The inner faces of the cavity are lubricated by fluid to ease breathing movements.

Pleural Cavity: The cavity formed between the pleural layer surrounding the lungs and the other layer lining the chest wall.

Pneumonia: An infection in the lung.

Port: A device that is surgically placed in the body. It is used to administer intravenous fluids and chemotherapy. Blood tests can be withdrawn through the device also.

Precancerous: Abnormal cellular changes that have the potential to become malignant (cancerous).

Preleukemia: A condition in which the bone marrow does not function normally. It does not produce enough blood cells. This condition may progress and become acute leukemia. Preleukemia also is called myelodysplastic syndrome or smoldering leukemia.

Preliminary Search: The process by which a patient's HLA type is sent to donor registries so that it can be compared to the HLA types of all volunteers listed in the registry at that time. The patient's basic disease status are also submitted at preliminary search. The preliminary search becomes formal when specific donors are requested for further testing on behalf of the patient.

Pre-Transplant Conditioning: A regimen of chemotherapy with or without radiation therapy that destroys a patient's underlying cancer and bone marrow. The marrow is then restored by transplanting stem cells.

Prevalence: The percentage of the population that is affected by a certain disease (such as cancer) at a specific time.

Prevention: Reducing the number of cases of cancer by avoiding the substances, exposures or habits that are known to cause cancer.

Primary Tumor: The place where a cancer started. A patient may have cancer that started in the breast and spread to the bone, but the primary tumor is still in the breast.

Prognosis: The probable outcome or course of a disease; the chance of recovery.

Protocol: The outline or plan which specifies times and dosages for treatment methods such as surgery, chemotherapy or radiation therapy. Various tests at specific times may also be part of the protocol.