DNA flow cytometric analysis of neuroblastoma: distinction of tetraploidy subset

Neuroblastoma has several characteristics that differentiate it from other adult malignancies. The ploidy pattern of neuroblastoma has been shown to be related to prognosis. Specifically, a DNA diploidy pattern is associated with a poorer outcome, and an aneuploidy pattern is associated with a better outcome. A tetraploidy pattern has also been identified; however, there is little information regarding this pattern. To examine the properties of neuroblastoma according to these DNA ploidy patterns, the authors performed flow cytometric analysis (retrospectively) for 61 neuroblastoma cases, using paraffin-embedded tissues. Fifty-six of the cases had analyzable results. Calculated DNA indices (DI) ranged from 1.0 to 2.30. The 56 cases were divided into three groups according to DI: diploid (DI = 1.0 to 1.17, n = 19), aneuploid (DI = 1.25 to 1.75, n = 26), and tetraploid (DI = 1.81 to 2.30, n = 11) groups. Compared with the aneuploid group, the diploid group had a stronger correlation with older patient age (> or = 1 year) (P < .01), more advanced clinical stage (III, IV) (P < .01), and poorer prognosis (P < .001). The tetraploid group had properties that were statistically similar to those of the diploid group (P < .05, P < .05, P < .001, respectively). These findings indicate that a subset of DNA tetraploid is present in neuroblastoma, and this subset, which may have clinical and biological characteristics similar to those of the DNA diploid group, should be distinguished from DNA aneuploidy.