Lymphosarcoma is a malignant tumor in lymphatic tissue, caused by the growth of abnormal lymphocytes. lymphosarcoma cell leukemia has been used to describe the invasion of blood by other types of lymphoma, including large cell, lymphoblastic, and Burkitt's lymphoma, although these are better designated as the particular lymphoma in leukemic phase. When abnormal cells appear in the blood samples of patients with lymphoma, acute myelogenous leukemia must also always be considered, particularly in patients who have received substantial prior chemotherapy or irradiation.