Walsh & Hoyt: Leukemia: Pathology

The pathologic alterations in all types of leukemia may be divided into two types: (a) those that are produced by the proliferation of leukemic cells within the blood-forming organs, particularly the bone marrow, spleen, and lymph nodes; and (b) those that are produced by infiltration of leukemic cells in other organs. Fatigue, pallor, and headache ensue. The bone marrow is invariably hyperplastic and reddish gray, whereas the degree of cellular proliferation in, with consequent enlargement of, the lymph nodes and spleen varies with the different types of leukemia. In organs that become infiltrated during the leukemic process, it is common to observe destruction of normal tissue and replacement by masses of leukemic cells. Organs most likely to be affected include the liver, lungs, kidneys, and gastrointestinal tract.