Differentiation Between Sarcomatous and Leukemic Lymphocytes in Mice *

The question as to whether human leukemia is to be classified as a neoplasm or as an atypical hyperplastic response of the hemopoietic tissues to an unknown agent has been the subject of much speculation. The lymphosarcomata have been classified with the leukemias by many investigators because of the obvious similarity certain cases of leukemia bear to true neoplasms. The atypical cells of leukemia usually show an extremely generalized distribution, whereas the lymphosarcomatous cells exhibit local infiltrative growth with more or less discrete foci of metastasis. Thus, leukemia has been considered by many to be a "systemic disease" (hyperplastic or neoplastic) with multicentric foci of origin, whereas the sarcomata are said to be neoplasms of unicentric origin with or without metastases."' 15 With the experimental study of leukemia and lymphosarcoma in guinea-pigs and mice, much progress has been made in-acquiring a more clear-cut understanding and classification." 12,'13 14 On the basis of transplantation experiments, leukemia in these animals has definitely been demonstrated to be a neoplastic disease. The nature of the growths (lymphosarcomatous or leukemic) resulting from inoculation of different lines of neoplastic lymphocytes into uniform hosts is described in this paper. Variations in the behavior of different neoplastic lymphocytes in the same environment might afford a basis for differentiation between lymphosarcoma and leukemia.