tions and perform postmortem analysis. A brief discussion of the pertinent discoveries that occurred more than 100 years ago gives one a great appreciation of just how far the science of hematology has progressed in such a short time. Two scientists in separate countries made early descriptions of leukemia in 1845. Bennett in Scotland and Virchow in Germany both studied a series of autopsy findings from individuals who died with very enlarged spleens and livers (hepatosplenomegaly).1,2 Virchow is credited with assigning the term weisses blut (meaning "white blood"), which is translated into Greek as leukemia. Both Bennett and Virchow came to believe that leukemia is caused by a cancerous overgrowth of the white cells. Virchow was able to demonstrate by further studies that one could classify the cases into two groups: those with mostly large spleens and those with predominantly enlarged lymph nodes.3 We now know that these groups represent a distinction between chronic myelocytic leukemia (CML) and chronic lymphocytic leukemia (CLL).
The next conceptual proposal came in 1878 from Neumann, who suggested that the origin of blood cells was the bone marrow, and hence leukemia was a disease of the bone marrow. He used the term myelogene, which is the origin of the later term "myelogenous leukemia."4 Epstein in 1889 was the first to assign the term acute leukemia, designating cases wherein the patients died from the disease in a matter of months from manifestation of first symptoms. He noted that these patients had very purulent blood and surmised by this gross observation of white blood that there was an incredible increase in white cells. He was eventually able to lead the hematology forefathers of his day to recognize a separation between what we now call acute myelogenous leukemia (AML) and a more chronic, slow onset that we now recognize at CML.5
Proof of the early scientist's ingenuity is the fact that until Ehrlich developed a polychromatic stain in 1877 that allowed blood cells to be distinguished, scientists were only able to observe colorless cells under the microscope6! Once the use of his stains became widespread around the turn of the century, scientists were able to show that acute leukemia was associated with early blast cells, and chronic leukemia with more mature cells. Thus, in 1900 the description of a myeloblast and a myelocyte were documented by Naegeli,7 and several years later the existence of monoblastic leukemia was first described by Schilling. Hirschfield's important contribution was that he made the connection that red cells and white cells share a common cell of origin.8 The combined discoveries of these scientists laid the foundation for our current understanding of leukemia. As new research and application of new techniques continue to refine the classification of leukemia, changes in treatment protocols lead to improved survival statistics.
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