Primary myelosarcomas are associated with a high rate of relapse: report on 34 children from the acute myeloid leukaemia-Berlin-Frankfurt-Münster studies.

Primary myelosarcomas are rare manifestations of acute myeloid leukaemia (AML) that precede bone marrow involvement. Out of 744 children observed during the AML-Berlin-Frankfurt-Münster (BFM) studies 87 and 93, 34 children presented with extramedullar myelosarcomas and no blasts (n = 21; 2.8%), or a low blast count (n = 13; 1.7%) in the bone marrow. Owing to the initially mild and variable symptoms, in some children (n = 12) diagnostic procedures were delayed and treatment intensity was reduced. At 0.65 +/- 0.13, the cumulative incidence of relapse was significantly higher than in other AML patients (0.28 +/- 0.02). The 5-year event-free survival was 0.19 +/- 0.08 (compared with 0.48 +/- 0.02 in AML-BFM studies 87/93; P(log rank) < 0.03). Overall, 18 out of 34 patients died from disease (estimated 5 year survival 0.44 +/- 0.09 compared with 0.55 +/- 0.02 in the AML-BFM-studies 87/93; P(log rank) = 0.35, n.s.). An early diagnostic workup is needed in children with unusual skin lesions or tumours, considering myelosarcoma as a primary manifestation of AML. Intensive AML-specific chemotherapy is recommended soon after diagnosis.