ABSTRACT
Diffuse large B-cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphoma (NHL), representing up to 30 percent of all lymphomas. DLBCL is a fast-growing, aggressive form of NHL, which can appear as a transformation from a less aggressive form of lymphoma or can be de novo pathology. The following article describes the case of a 55-year-old female patient who developed a DLBCL as a second malignancy after an R-CHOP-treated marginal zone splenic lymphoma. This was followed by the transformation of the DLBCL into an ag- gressive acute lymphoblastic leukemia, for which the patient needed aggressive treatment according to the international acute lymphoblastic leukemia protocol.