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a term used until the mid-1970’s to designate any one of various tumors of the blood system and some types of leukemia and hereditary disease involving the accumulation of lipids. The use of the term was based on the hypothesis that hematopoietic cells originate from reticular-tissue cells; it was also based on a certain morphological resemblance between tumor cells and normal reticular cells. Since it has been established that the formed elements of the blood originate from a mobile lymphocyte-like stem cell while the cells of bone-marrow stroma have their own precursors, the term “hemoblastosis” is now used in the medical literature to designate various types of tumors of hematopoietic tissue. The term “reticulosis” now refers only to tumors originating from cells of bone-marrow stroma and of the lymphatic system. Thus, reticuloses do not include leukoses, since reticular cells are not hematopoietic. Reticuloses also do not include reactive proliferations of reticular cells in tuberculosis, sepsis, infectious mononucleosis, and collagen diseases because these processes do not have the characteristics of malignant growth.