A-5-year old boy was presented because of decreasing physical fitness, pallor, and discrete left lower eye-lid hematoma. Clinical examination detected a palpable mass 4 cm below the left costal margin. Blood analysis showed leukopenia, normochromic, normocytic anemia, thrombocytopenia, no irregular differential count, elevated LDH, hypofibrinogenemia, and elevated d-dimers. Acute leukemia was suspected and a bone marrow (BM) aspirate performed showing >90% infiltration with small blue round cells (Panel A, B). Massive elevated serum values of homovanillic and vannillylicmandelic acid confirmed a diagnosis of neuroblastoma. Neuroblastoma arising as in this case from the adrenal gland represents the most frequent solid tumour in young childhood. BM infiltration is common, however, diffuse massive infiltration without any or markedly reduced tendency to aggregate is observed less frequently and associated with a poorer prognosis. Typically tumour cells appear arranged in balls or rosettes with a granular central era. However, this classical pattern was observed only at single spots of the smears (Panel A). In stage IV disease the BM may be the only sample obtained necessarily for establishing the diagnosis also allowing detection of established prognostic genetic markers (e. g. MYC-N). Stefani Parmentier, M.D. University Hospital Dresden, Medical Department I, Germany Stefani.Parmentier@uniklinikum-dresden.de Meinolf, Suttorp, M.D. University Children´s Hospital Dresden, Germany Meinolf.Suttorp@uniklinikum-dresden.de