Two Cases of Neuroblastoma with Genotype–Phenotype Discordance: Clinical Management According to Histological Subtype and N-myc Expression

MYCN-amplified neuroblastoma demonstrating favorable histology, which is genotype–phenotype discordant, is extremely rare. This study reports two cases of peripheral neuroblastic tumors with genotype–phenotype discordance: a 3-month-old female and 10-month-old male patients with stage 4S and 2B neuroblastoma, respectively, harboring MYCN-amplification and favorable histology. Immunohistochemical staining was negative for N-myc. Both patients were treated with conventional chemotherapy and 13-cis-retinoic acid without autologous stem-cell rescue, and have been disease-free for 74 and 38 months post-resection, respectively. Nevertheless, chemotherapy could have been optimized on the basis of histological features of the tumors, showing no expression of N-myc.