Leukemoid Crisis or Reaction: A temporary appearance of immature leukocytes in
the blood stream, with a marked increase in the total white count. In the laboratory
sometimes temporarily indistinguishable from leukemia.
Leukocyte: White blood cell.
Leukocytosis: An increase in leukocytes in the blood.
Leukopenia: A reduction in the number of leukocytes in the blood.
Leukopoiesis: Leukocyte formation.
Lymphoblast: The parent cell of the lymphocytic series.
Lymphocyte: A white blood cell having a round or oval nucleus and sky blue
cytoplasm. The nuclear chromatin is densely clumped but separated by many clear
areas giving a "hill and valley" effect. A few red-purple (azurophilic) granules may be
present in the cytoplasm.
Lymphocytosis: A relative or absolute increase in the number of circulating
Lymphopenia: An abnormal decrease in the number of lymphocytes.
Lysis: Destruction by a specific agent.
Macrocyte: An erythrocyte larger than normal.
Macrocytosis: An increase in the number of macrocytes.
Mast Cell: A basophil or a true tissue cell.
Maturation Factor: A substance that will cause cells to ripen and care to maturity.
Mean Corpuscular Hemoglobin (MCH): The average amount of hemoglobin in the
red blood cell.
Mean Corpuscular Hemoglobin Concentration (MHC): The average percent
hemoglobin saturation in the red blood cell.
Mean Corpuscular Volume (MCV): The volume of the average red blood cell.
Megakaryoblast: The parent cell of the megakaryocytic series.