Neuroblastomas with discordant genotype-phenotype relationships: report of four cases with MYCN amplification and favorable histology.

ABSTRACT MYCN amplification prevents cellular differentiation and promotes mitotic and karyorrhectic activities in neuroblastomas. Hence, MYCN-amplified tumors typically show an appearance of neuroblastoma of either an undifferentiated or a poorly differentiated subtype with a high mitosis-karyorrhexis index. In addition, they are classified as part of the unfavorable histology group, according to the International Neuroblastoma Pathology Classification. Large cell type and/or presence of prominent nucleoli is also reported to be an additional hallmark of MYCN amplification. However, there are few neuroblastomas having MYCN amplification and favorable histology. Four cases of MYCN amplification and favorable histology were identified in our file of 63 cases of neuroblastoma. The patients (M∶F  =  3∶1) were diagnosed between 6 and 13 months of age, and all had adrenal primary tumors and were treated with high-dose therapy and autologous stem cell rescue. Three patients (stages 1, 3, and 4) are alive and we...