Abstract
Neuroblastoma is the second most common solid tumor occurring in children. Amplification of the MYCN oncogene is associated with poor prognosis. To identify neuroblastoma tumors with MYCN amplification, we studied the number of copies of MYCN in interphase cells by fluorescence in situ hybridization in 20 neuroblastoma patients. MYCN amplification appeared in 7 tumor specimens. Interphase and metaphase studies showed a tumor cell population with both forms of amplification, double minutes and homogeneously staining regions, in two patients. These patients showed a smaller tumor cell subpopulation with the presence of more than one homogeneously staining region, suggesting that gene amplification was undergoing karyotype evolution.