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The Leukemia/Bone Marrow Transplant Program of BC

Hematology Dictionary
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P

Packed Cell Volume
Measurement of the proportion of the blood occupied by the red blood cells. Normal values are 40-54% in males, 35-47% in females.

Palliative Care
Treatment aimed at relieving symptoms and pain rather than affecting a cure. Pancytopaenia Condition in which there are reduced numbers of all types of blood cells.

Paraprotein (malignant)
Malignant paraprotein is a form of antibody characteristic of, and produced by, malignant cells of the mature B-cell type, for example in multiple myeloma. Its presence in the blood acts as an important marker of disease.

Paroxysmal Nocturnal Haemoglobinuria (PNH)
A rare disorder characterized by an increased rate of break- down of red blood cells and decreased production of white blood cells and platelets. This leads to excretion of the red blood pigment, hemoglobin, in the urine, particularly at night. The cause is unknown and the severity of disease variable.

Pathogenesis
Development of a disease.

Pathologist
A doctor who specializes in the cause and diagnosis of disease and how disease affects the organs of a body.

Peripheral Blood Stem Cell
There are small numbers of stem cells in the circulation. These are known as Peripheral Blood Stem Cells (PBSC).

Peripheral Blood Stem Cell Transplant
The use of peripheral blood stem cells as an alternative to bone marrow transplantation. The stem cells are obtained by using growth factors to increase numbers in the circulation to a level where they can be harvested.

Petechiae
Small red or purple pinhead spots on the skin. They are small hemorrhages and usually the result of a shortage of platelets.

Pharmacokinetics
The study of the action of a drug in the body over a period of time, including the processes of absorption, metabolism and excretion.

Phenotype
The characteristic appearance and function of a cell or tissue.

Philadelphia Chromosome
An abnormal chromosome associated with chronic myeloid leukemia and some cases of acute lymphoblastic leukemia. The Philadelphia chromosome is formed when part of chromosome 9 attaches to chromosome 22. This abnormality is found in nearly all cases of chronic myeloid leukemia.

Plasma Cells
Large cells derived from the lymphocytes that form antibodies. Not normally found in circulating blood but restricted to bone marrow and lymph nodes.

Plasma Cell Leukemia
The end stage of myeloma when immature plasma cells are found circulating in the blood.

Plasmacytoma A localized area of myeloma-like disease, either in a bone or in the other tissues of the body. If there is only one such area it is called solitary plasmacytoma.

Plateau Phase
Stable stage of disease in lymphoma following good response to anti-cancer treatment.

Platelets
Tiny cell-like bodies derived from megakaryocytes in the bone marrow. Circulate in the blood and play an important role part in the prevention and control of bleeding. Normal values, 150-400 x 109 per liter.

Polycythaemia Rubra Vera (PRV)
A condition characterized by the over-production of red blood cells by the bone marrow. Diagnosis is based on an increased number and volume of red cells. The total number of white blood cells and platelets may also be increased. Treatment will vary according to the age of the patient and severity of the disease. This condition carries an increased risk of developing acute leukemia.

Portacath
A form of central venous line in which the whole of the line is surgically implanted within the body, unlike a "HICKMAN"® catheter. A membrane just below the skin gives access by a simple skin puncture to a line running straight into one of the main blood vessels. This simplifies the administration of chemotherapy. "HICKMAN"® is a registered trademark of C.R. Bard, Inc. and its related company, BCR, Inc.

Preleukemia
A general term referring to some non-cancerous blood disorders, such as myelodysplasia, which carry an increased risk of the patient developing acute leukemia. The expression is misleading because only a minority of patients with these conditions develops leukemia.

Progenitor Cell or Precursor Cell
Immature cell in the bone marrow, which is responsible for producing mature blood cells.

Prognosis
An assessment of the likely benefits of treatment for a patient, particularly concerning the chances of cure and complete recovery.

Prolymphocyte
An early lymphocyte precursor. Not commonly seen in the blood but in prolymphocytic leukemia they may be present in large numbers.

Prolymphocytic Leukemia
A variant of chronic lymphocytic leukemia in which the malignant cells have a more immature appearance. The disease requires chemotherapy and/or radiotherapy and sometimes removal of the spleen (splenectomy).

Prophylaxis
Precautionary treatment given with the aim of preventing a disease occurring.

Protocol
A schedule of treatment. For example, the number, frequency and timing of administration of a course of anti-cancer drugs.

Pruritis
Itching, sometimes severe, which may be a significant problem in lymphoma.

Purging
The laboratory treatment of bone marrow harvested for an autologous bone marrrow transplant or peripheral blood stem cell transplant to remove any residual leukemic cells in order to reduce the theoretical chance of relapse. The use of this procedure varies between treatment centers and depends on the type of leukemia being treated.

Purpura
A condition characterized by the occurrence of purple spots on the skin, often accompanied by bleeding from the gums.

 

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The information in this glossary is cited with permission from the Leukemia Research Foundation web site.

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