[Acute leukemia in a 13-year old boy with a synchronous occurrence of lympho- and monoblasts (author's transl)]

The synchronous occurrence of blasts of the lymphatic and myelogenous lineage in acute leukemia has been rarely observed. Reviewing individual case reports it is suggested that malignant transformation already starts at the level of the stem cell. We are reporting a case of a 13-year old boy who initially showed morphological features of acute lymphatic leukemia. Following 14 days of therapy the assumption of a pure lymphatic lineage has to be changed in favour for monoblasts which are now occurring.