Glossary E

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Engraftment: The process of infused donor stem cells homing to the marrow of a recipient and producing blood cells of all types. Engraftment is first evident when new white cells, red cells and platelets begin to appear in the recipient's blood following stem cell transplantation.

Eosinophil: A type of white blood cell that participates in allergic reactions and helps to fight certain parasitic infections.

Eosinophilia: Increased numbers of eosinophils in the blood.

Epidemiology: The study of disease in populations. These studies relate the incidence and prevalence of disease to genetic and environmental factors.

Erythroleukemia: A sub-type of acute myelogenous leukemia in which in its initial phase the leukemic cells are composed principally of erythroblasts often with very striking structural aberrations.

Essential Thrombocythemia: A clonal abnormality initiated by the transformation of a multipotential hematopoietic cell in the marrow. Its principal effect is the production of exaggerated numbers of platelets. The accumulation of platelets in the blood can be three to thirty times normal. Signs of the disease include a predisposition to inappropriate thrombosis and hemorrhage. Parodoxically, too many platelets may foster clotting and also predispose to bleeding. In part, this is explained by a failure of platelets to function normally in hemostasis when present in very high numbers. Drugs to lower the platelet count may be required in symptomatic patients.

Extramedullary myeloma: A tumor of plasma cells in a site other than the marrow. Although this tumor may occur in any location, it usually is in the head, around the eyes or the paranasal sinuses. It may be accompanied or followed by evidence of myeloma in the marrow.

Extranodal Lymphoma: Primary extranodal lymphoma is the term used when a lymphoma appears to originate in a site other than a lymph node. Virtually every organ can be the site of origin of an extranodal lymphoma. The stomach and intestines, brain, thyroid gland, testis, urinary tract, skin, bone, lung, and others may be the first site at which malignant lymphocytes accumulate and form a tumor. Extranodal lymphoma may accompany lymph node involvement at the time of diagnosis or later. The latter situation usually is a harbinger of a progressive type of lymphoma.