Finally, in patients with "primary" leukemia cutis who have been treated with this granulocyte-colony stimulating factor, it is possible that the atypical cells of leukemia cutis developed into mature neutrophils of Sweet's syndrome as a result of granulocyte-colony stimulating factor therapy-induced differentiation of the sequestered leukemia cells [205]. The gene discussed is CSF3; the disease is leukemia.