Isolated myelosarcomas are rare first manifestations of acute myeloid leukemia (AML), preceding bone marrow involvement by weeks to months. Seventeen of 654 children observed during the studies AML-BFM 87 and 93 were diagnosed as extramedullar myelosarcomas (2.6%). The predominantly myelomonocytic or monoblastic tumor cells (M4 or M5 according to FAB classification) mainly infiltrated skin (n = 8). Additional tumors were located in mucosa (n = 2), central nervous system (n = 2), orbita (n = 2), bone (n = 1), glandulae parotis (n = 1) and lymph nodes. Due to the initial mild and variable symptoms in some children the diagnostic measurements were delayed and treatment was inadequate. This might be responsible for the high rate of relapse (79%) and the poor outcome. Ten of 17 patients died from disease (estimated survival 0.27 +/- 0.13 compared to AML-BFM 87/93 0.51 +/- 0.03). Suspect skin lesions or tumors should be considered as isolated myelosarcoma of a primary manifestation of AML. An intensive AML-specific chemotherapy is recommended.
