(2) Subleukemic leukemia; white blood count is less than 15,000 WBC per
cu mm with immature or abnormal forms of white cells present in the peripheral blood.
(3) Aleukemic leukemia; white blood count is less than 15,000 WBC cu mm
with no immature or abnormal white cells present in the peripheral blood. The
distinction between subleukemic and aleukemic leukemia will depend mostly on a
thorough search for abnormal cells.
c. Another classification is based on the type and the maturity of the cells found
to be predominant in the blood and bone marrow. In most cases, classification by cell
type makes it possible to distinguish between lymphocytic, neutrophilic, and other
leukemias. In acute blast cell leukemia a pure population of blast cells is seen, and the
cell type usually cannot be identified. Classification according to cellular maturation will
often parallel the classification according to duration; acute leukemias show a large
number of immature cells while the chronic cases have a significant number of well-
differentiated cells. Morphologically, a "subacute" leukemia will usually resemble the
acute stage more readily than the chronic condition.
4-17. TYPES OF LEUKEMIA
Several of the more common types of leukemia are discussed below:
a. Acute Lymphocytic Leukemia. At the time of diagnosis, the white count is
usually noticeably elevated, with 60 percent or more lymphoblasts and some
prolymphocytes present. Severe anemia and thrombocytopenia are characteristic. The
lymphoblasts have a round or oval nucleus composed of coarse granular or stippled
chromatin and usually contain one or two nucleoli.
b. Chronic Lymphocytic Leukemia. The white count is usually 20,000 to
200,000 per cu mm, with the peripheral blood smear showing 60 to 95 percent
lymphocytes. These cells are generally the small type of mature lymphocyte that often
show a small cleft or indentation in the shape of the nucleus. Lymphoblasts are
generally absent from the peripheral blood but a rare prolymphocyte may sometimes be
found. These lymphocytes are somewhat more fragile than normal, resulting in many of
the cells appearing to be entirely devoid of cytoplasm. A normocytic, normochromic
anemia generally develops as the disease progresses. The platelet count is usually
c. Acute Myelogenous Leukemia. The white blood count usually shows
moderate to marked elevation with 60 percent or more of the cells being myeloblasts.
Auer rods may or may not be present in the cytoplasm of these cells. Some cases of
this disease show micromyeloblasts, a much smaller myeloblast than normal. Severe
normocytic, normochromic anemia develops, along with thrombocytopenia. The
platelets that are present may be large and bizarre-looking.