Ultrastructural features of neuroblastic tumours in relation to morphological, and molecular findings; a retrospective review study.

Background: Neuroblastoma is the most common solid tumour of infancy and is responsible for 15% of childhood cancer deaths. Presence of amplified MYCN in neuroblastoma is associated with poor prognosis and rapid tumour progression. The aim of this study was to examine and compare the ultrastructural features of high-risk MYCN amplified neuroblastomas, with lower-risk non-MYCN amplified tumours.

Methods: This was a retrospective study evaluating archival diagnostic tissue samples, in which Fluorescence in-situ hybridisation (FISH) had been used at diagnosis to establish MYCN status. 22 (11 MYCN amplified tumours and 11 non-MYCN amplified) tumours of similar light microscopic appearance (poorly differentiated neuroblastoma) were then selected for ultrastructural examination.

Results: There is a relationship between ultrastructural features in neuroblastoma and MYCN status, although with marked overlap between groups. MYCN amplified tumours generally exhibited a 'less differentiated' ultrastructural phenotype, with significantly smaller neurotubules (NT) in the cell body (p < 0.002). Non-MYCN amplified tumours show increased features of neuronal differentiation, with fewer neurosecretory granules (NSG) and NT in the cytoplasm.

Conclusions: MYCN amplification is associated with a less differentiated ultrastructural phenotype, and lack of MYCN amplification with relative ultrastructural neuronal differentiation.