Lymphoblast

Lymphoblasts are immature cells which typically differentiate to form mature lymphocytes. Normally lymphoblasts are found in the bone marrow, but in acute lymphoblastic leukemia (ALL), lymphoblasts proliferate uncontrollably and are found in large numbers in the peripheral blood.

The size is between 10 and 20 μm.

Although commonly lymphoblast refers to a precursor cell in the maturation of leukocytes, the usage of this term is sometimes inconsistent. The Chronic Lymphocytic Leukemia Research Consortium defines a lymphoblast as "A lymphocyte that has become larger after being stimulated by an antigen. Lymphoblasts look like immature lymphocytes, and were once thought to be precursor cells." . Commonly, when speaking about leukemia, "blast" is used as an abbreviation for lymphoblasts.

Lymphoblasts can be distinguished microscopically from myeloblasts by having fewer nucleoli than do myeloblasts, and the nuclear chromatin is more condensed, and cytoplasmic granules are absent.

Additional images
They are 2.5 micrometres in size.