Preconceived ideas in the classification of leukemia

General biological classifications have theoretical aims regarding the natural order of things. Classification in pathology has basic pragmatic aims regarding diagnosis, prognosis and treatment. In history, leukemia classifications were mainly (but not exclusively) based on classification of normal cells. Clinical data were introduced mainly secondarily. For a long time, no treatment was available. Two questions are asked: might classification of leukemia help to understand the disease's mechanisms; might better classification eliminate unclassifiable leukemias?