Transient increase in blasts mimicking acute leukemia and progressing myelodysplasia in patients receiving growth...

Previous studies of the hematologic effects of granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) have emphasized the morphologic changes induced by these growth factors, but few have reported increases in blasts. Here, we report six cases in which growth factor treatment resulted in a marked but temporary increase in peripheral and bone marrow blasts that led to diagnostic confusion with acute leukemia and high-grade myelodysplastic syndromes. Five of the six patients were receiving treatment for hematologic malignant neoplasms, and one patient had an optic nerve germinoma. Growth factor treatment included single agent therapy with G-CSF (three patients), GM-CSF (one patient), or simultaneous therapy with G-CSF and GM-CSF (two patients). In two patients, there was a dramatic increase in blasts in the peripheral blood (39% and 20%), whereas four had substantial increases in blasts on the aspirate smear (8%-41%). One patient had a medium-sized blast cluster shown on the core biopsy specimen. The blasts decreased after removal of growth factor in all patients. The findings indicate that growth factor therapy can cause a substantial transient increase in blasts in the bone marrow and peripheral blood that may be confused with relapse of acute leukemia or progression of a myelodysplastic syndrome.