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extramedullary tissues—especially in the lymph nodes,

spleen, and liver.

In myelogenous leukemia, the cancerous process

occasionally produces partially differentiated cells,

resulting in what might be called neutrophilic

or monocytic leukemia. More frequently, however, the

leukemia cells are bizarre and undifferentiated and

not identical to any of the normal white blood cells.

Usually, the more undifferentiated the cell, the more

acute is the leukemia, often leading to death within a

few months if untreated.With some of the more differentiated

cells, the process can be chronic, sometimes

developing slowly over 10 to 20 years. Leukemic

cells, especially the very undifferentiated cells, are

usually nonfunctional for providing the normal protection

against infection.

The first effect of leukemia is metastatic growth of

leukemic cells in abnormal areas of the body.

Leukemic cells from the bone marrow may reproduce

so greatly that they invade the surrounding bone,

causing pain and, eventually, a tendency for bones to

fracture easily.

Almost all leukemias eventually spread to the

spleen, lymph nodes, liver, and other vascular regions,

regardless of whether the origin of the leukemia is in

the bone marrow or the lymph nodes. Common effects

in leukemia are the development of infection, severe

anemia, and a bleeding tendency caused by thrombocytopenia

(lack of platelets). These effects result

mainly from displacement of the normal bone marrow

and lymphoid cells by the nonfunctional leukemic

cells.

Finally, perhaps the most important effect of

leukemia on the body is excessive use of metabolic

substrates by the growing cancerous cells. The

leukemic tissues reproduce new cells so rapidly that

tremendous demands are made on the body reserves

for foodstuffs, specific amino acids, and vitamins. Consequently,

the energy of the patient is greatly depleted,

and excessive utilization of amino acids by the

leukemic cells causes especially rapid deterioration of

the normal protein tissues of the body.Thus, while the

leukemic tissues grow, other tissues become debilitated.

After metabolic starvation has continued long

enough, this alone is sufficient to cause death.