[Extramedullary blast crisis of mixed precursor T lymphoblastic and myeloblastic features in a patient with chronic myelogenous leukemia successfully treated with low-dose oral etoposide].

A 47-year-old man presented with fever, cough and chest pain in January, 1989. He was found to have mediastinal tumor and generalized lymphadenopathy. Peripheral blood and bone marrow findings were typical for the chronic phase of chronic myelogenous leukemia (CML). Although the histological findings of a cervical lymph node were indistinguishable from those of malignant lymphoma, cytogenetic studies of the lymph node cells showed positive Ph1 chromosome and rearrangement of the bcr gene as well as bone marrow cells. Double fluorescence analysis of lymph node cells demonstrated co-existence of CD5, CD7 and CD33 positive cells and of cells sharing both CD5 or CD7 and CD33 antigens. These findings suggest that tumor cells originate from the stage at which the differentiation pathways of hematopoietic stem cells branch into precursor T and myeloid cells. Various combination chemotherapies had only partial effects on lymph node swelling. Chronic daily administration of low dose etoposide was very effective to control both lymphadenopathy and leukocytosis and the patient remained well for over 2 years until July, 1991 when hematological myeloid blast crisis developed. He died of pneumonia in October, 1991. This is a rare case of CML with extramedullary mixed crisis which survived for a long time.