Subcritical N-myc amplification and DNA index in aneuploid neuroblastoma

N-myc gene amplification > 10-fold is associated with < 5% of patients with disease-free survival at 18 months. Aneuploidy is associated with good prognosis. An inverse relationship should be expected between the two parameters if no other dependent parameters mediate prognosis, that is, a relationship between treatment sensitivity and proliferation rates. Our aim was to assess the relationship between N-myc replication and aneuploidy in neuroblastoma. Tumor samples of 12 consecutive unselected, karyotypically confirmed, aneuploid neuroblastomas were submitted for N-myc amplification by DNA digestion with restriction endonuclease EcoRl and standard Southern blot analysis. Relationship between copy number and degree of aneuploidy as expressed by DNA index was studied by graphic statistical analysis. Four cases had no measurable amplification of the N-myc locus (DNA indices: 1.73,1.94,1.44,1.51); three cases had three or four copies of N-myc (DNA indices: 1.92, 2.07) ; one case had five copies (DNA index: 1.45). In five cases samples proved unrepresentative on frozen section verification of stored material. In human, aneuploid neuroblastoma, subcritical N-myc amplification is not clearly related to (degree of) DNA aneuploidy. Copyright © 1997 Taylor & Francis.