Acute monoblastic leukemia: a unique subtype--a review from the Childrens Cancer Study Group

The acute non-lymphocytic leukemias (ANLL) are generally treated as a homogeneous group. However, the literature is replete with articles alluding to distinctive features of acute monoblastic leukemia (AMoL). This review addresses the unique clinical, laboratory, epidemiological, and therapeutic features of AMoL. Leukemic monoblasts are distinguished from other cells in the myelocytic series by physical properties such as greater adhesiveness, deformability, and motility. Patients with AMoL often exhibit hyperleukocytosis, disseminated intravascular coagulation, and extramedullary involvement, particularly in the skin, gingiva, and central nervous system (CNS). AMoL occurs predominantly in adults over 40 and children under 10, fifty percent of whom are under 2 years of age at diagnosis. Its relatively common occurrence in infants parallels the high rate of proliferation of monocytes in that age group. Additionally, its occurrence in young children appears to be associated with in utero exposure to marijuana and parental exposure to pesticides and solvents. Therapeutic results are generally poor due to high rates of fatal complications during induction, induction failures, and frequent extramedullary and medullary relapses. This poor outcome is particularly noted in infants. Higher remission induction rates attained with epipodophyllotoxins and incorporation of bone marrow transplantation have not yet resulted in substantial improvement of long-term outcome. Recurrence of disease in the CNS is minimized by the use of intensive CNS presymptomatic treatment, usually incorporating irradiation. Our review suggests that unique and innovative treatment strategies are needed to improve outcome for patients with AMoL.